Why Do Lithium–Oxygen Batteries Fail: Parasitic Chemical Reactions and Their Synergistic Effect

Yao, Xiahui; Dong, Qi; Cheng, Qingmei; Wang, Dunwei

doi:10.1002/anie.201601783

Cited by 208 publications

(205 citation statements)

References 96 publications

(326 reference statements)

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“…[1,2] Among these novel battery systems, the aprotic lithium-air (Li-O 2 ) battery has received by far the most scrutiny because of its highest theoretical specific energy than any other rechargeable batteries. [5,10,11] Carbon materials are widely used to prepare oxygen electrodes for Li-O 2 batteries owing to their unique properties such as high electronic conductivity, light weight, low cost, and abundant resources. [6][7][8][9] One of the obstacles is the chemical and electrochemical instability of the oxygen electrode under Li-O 2 operating conditions, where reactive oxygen species (O 2 − , LiO 2 , and Li 2 O 2 ) that are destructive to battery components are incessantly generated.…”

Section: Doi: 101002/adma201606816mentioning

confidence: 99%

Hierarchical Porous Carbon Spheres for High‐Performance Na–O₂ Batteries

et al. 2017

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As a new family member of room-temperature aprotic metal-O batteries, Na-O batteries, are attracting growing attention because of their relatively high theoretical specific energy and particularly their uncompromised round-trip efficiency. Here, a hierarchical porous carbon sphere (PCS) electrode that has outstanding properties to realize Na-O batteries with excellent electrochemical performances is reported. The controlled porosity of the PCS electrode, with macropores formed between PCSs and nanopores inside each PCS, enables effective formation/decomposition of NaO by facilitating the electrolyte impregnation and oxygen diffusion to the inner part of the oxygen electrode. In addition, the discharge product of NaO is deposited on the surface of individual PCSs with an unusual conformal film-like morphology, which can be more easily decomposed than the commonly observed microsized NaO cubes in Na-O batteries. A combination of coulometry, X-ray diffraction, and in situ differential electrochemical mass spectrometry provides compelling evidence that the operation of the PCS-based Na-O battery is underpinned by the formation and decomposition of NaO . This work demonstrates that employing nanostructured carbon materials to control the porosity, pore-size distribution of the oxygen electrodes, and the morphology of the discharged NaO is a promising strategy to develop high-performance Na-O batteries.

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Section: Doi: 101002/adma201606816mentioning

confidence: 99%

Hierarchical Porous Carbon Spheres for High‐Performance Na–O₂ Batteries

et al. 2017

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“…© The Author The Li-air or Li-O 2 system has captured a scientific attention worldwide due to its high theoretical energy density, however many challenges in the electrochemistry of this system still remain to reach commercialization. [1][2][3][4] Those challenges have given rise to a fundamental understanding of the oxygen reduction reaction (ORR) mechanistic paths in lithium containing aprotic solvent systems. Interestingly, almost all electrochemical measurements relevant to the Li-air battery in the literature report a potential scale versus Li/Li + potential, very often without specifying the solvent, electrolyte salt and lithium concentration.…”

mentioning

confidence: 99%

Perspective—The Correct Assessment of Standard Potentials of Reference Electrodes in Non-Aqueous Solution

Mozhzhukhina

Calvo

2017

J. Electrochem. Soc.

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The challenges facing metal-air batteries have prompted fundamental studies of non-aqueous electrochemistry. However it appears that contributors in the field are not aware that the potentials of Li/Li + , Na/Na + , K/K + , and Mg/Mg 2+ electrodes depend on the nature of solvent due to the cation solvation. Therefore, it is imperative to define a clear potential scale that can be correlated in different solvents. Here we report on the strong effect of the solvent on the Li/Li + redox potential and discuss the use of the ferrocene/ferrocenium couple as internal or external standard for the measurements in non-aqueous solvents in lithium-ion and lithium-0 2 battery systems. © The Author The Li-air or Li-O 2 system has captured a scientific attention worldwide due to its high theoretical energy density, however many challenges in the electrochemistry of this system still remain to reach commercialization. [1][2][3][4] Those challenges have given rise to a fundamental understanding of the oxygen reduction reaction (ORR) mechanistic paths in lithium containing aprotic solvent systems. Interestingly, almost all electrochemical measurements relevant to the Li-air battery in the literature report a potential scale versus Li/Li + potential, very often without specifying the solvent, electrolyte salt and lithium concentration.Unlike in aqueous electrochemistry where the normal hydrogen electrode potential is the reference electrode of choice, in the lithium battery community the electrode potentials are referred to the Li/Li + system since in a lithium battery either the anode is Li metal or lithium intercalated in graphite with a redox potential very close to the metal Li/Li + electrode. Due to the strong solvation of the small lithium cation and the different electron donor capacity of different solvents, the electrode potential of Li/Li + couple strongly depends on the solvent used and it could vary by as much as half of a volt between dimethyl sulfoxide and acetonitrile. 5 Furthermore, in many reports while the potential scale is referred versus the Li/Li + , Li metal is not actually used as the reference electrode, but a different reference electrode such as Ag/Ag + is employed and then converted into the Li/Li + scale often without specifying how this was done. Current StatusBrowsing through the Li-air literature we can find that in 2009 Laoire et al. used aqueous Ag/AgCl reference electrode and repored their data versus this reference. However they also indicated that Ag/AgCl gives a potential of 2.93 V versus Li/Li + , as measured using a Li foil reference electrode in a LiPF 6 solution in organic carbonates. 6This is an example of the very rare case in the Li-air literature, where the results were reported versus actual reference employed as we can see later since almost all the literature refer to the Li/Li + scale. In 2010, the same authors used the Pt mesh as the reference electrode and reported their data versus Li/Li + . They argued that the Pt electrode was calibrated with reference to the ferrocenium ion/f...

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“…Moreover, compared to the Li-O 2 cell with bare Li metal, the cell using GPDL-coated Li metal exhibited the stable upper voltage plateau on discharge, indicating that the stable reaction of oxidation and reduction of RM itself is maintained without side reaction with Li metal confirming the successful protection of Li metal electrode by GPDL. [17,22,29,[54][55][56][57] To clearly indicate the effects and advantages of a GPDL on the Li metal electrode, various possible issues in Li-O 2 batteries are schematically described in Figure 3d,e. The energy efficiencies of the operated Li-O 2 cells as a function of cycle number are summarized in Figure 3c.…”

Section: Electrochemical Test Results For Li-o 2 Batteriesmentioning

confidence: 99%

Optimized Concentration of Redox Mediator and Surface Protection of Li Metal for Maintenance of High Energy Efficiency in Li–O₂ Batteries

Kwak

Park

Jung

et al. 2017

Advanced Energy Materials

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this problem, solid [4][5][6][7][8][9] and liquid [10][11][12][13][14][15][16] catalysts have been introduced in Li-O 2 batteries. However, solid catalysts such as noble metals have been reported to promote not only the reversible decomposition of Li 2 O 2 but also electrolyte decomposition. [17][18][19] In addition, when direct contact between the solid catalyst and Li 2 O 2 is prevented or the surface of the catalyst is covered with Li 2 O 2 , no catalytic activation effect is expected. [10,11] Alternatively, liquid catalysts, called redox mediators (RMs), [10][11][12][13][14][15][16] have been added to the electrolyte as electron-hole transfer agents to promote reversible Li 2 O 2 formation/ decomposition. RMs constitute a more efficient solution for charge-discharge reversibility, resulting in a reduction of the charge overpotential without severe electrolyte decomposition. However, it has recently been reported that RMs can be deactivated during cycling through chemical reduction at the Li metal electrode (self-discharge of the electrochemically oxidized RM) and attack by oxygen species at the cathode. [20][21][22] Thus, more stable RMs are still required for practical application of Li-O 2 batteries with longer cycle life and higher efficiency.To alleviate the aforementioned problems associated with RMs in Li-O 2 batteries, Li metal, which is an essential anode component for obtaining a high energy density, should be protected through surface treatment and the employment of functional separators. [20,[22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40] However, reported Li protection materials and Li-protective layers mainly consist of polymers, which have insufficient stiffness to suppress the growth of Li dendrites. These polymer materials can also be decomposed by reactive oxygen radicals that are produced as intermediates during the formation and decomposition of Li 2 O 2 . [29,41] Herein, we attempted to solve these problems by controlling the concentration of the RM (LiBr) in the electrolyte and using a stable and stiff Li metal protective layer (a graphenepolydopamine composite layer, GPDL), which can help maintain high efficiency over prolonged cycling in Li-O 2 batteries. An appropriate concentration of LiBr in diethylene glycol dimethyl ether (DEGDME) was used as the RM based on previous reports. [15,42] A graphene-polydopamine composite was developed as a protective layer and was uniformly coated onto the Li metal electrode to suppress undesired reactions with LiBr in the electrolyte, as well as with oxygen and moisture. Using these approaches, we successfully demonstrated high-efficiency Recently, various approaches for adding redox mediators to electrolytes and introducing protective layers onto Li metal have been suggested to overcome the low energy efficiency and poor cycle life of Li-O 2 batteries. However, the catalytic effect of the redox mediator for oxygen evolution gradually deteriorates during repeated cycling owing to its decomposition at the surfaces of both t...

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Why Do Lithium–Oxygen Batteries Fail: Parasitic Chemical Reactions and Their Synergistic Effect

Abstract: electrochemistry ·energy storage ·lithium-oxygen batteries ·r eactive oxygen species · synergistic effect

Cited by 208 publications

References 96 publications

Hierarchical Porous Carbon Spheres for High‐Performance Na–O₂ Batteries

Hierarchical Porous Carbon Spheres for High‐Performance Na–O₂ Batteries

Perspective—The Correct Assessment of Standard Potentials of Reference Electrodes in Non-Aqueous Solution

Optimized Concentration of Redox Mediator and Surface Protection of Li Metal for Maintenance of High Energy Efficiency in Li–O₂ Batteries

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Why Do Lithium–Oxygen Batteries Fail: Parasitic Chemical Reactions and Their Synergistic Effect

Abstract: electrochemistry ·energy storage ·lithium-oxygen batteries ·r eactive oxygen species · synergistic effect

Cited by 208 publications

References 96 publications

Hierarchical Porous Carbon Spheres for High‐Performance Na–O2 Batteries

Hierarchical Porous Carbon Spheres for High‐Performance Na–O2 Batteries

Perspective—The Correct Assessment of Standard Potentials of Reference Electrodes in Non-Aqueous Solution

Optimized Concentration of Redox Mediator and Surface Protection of Li Metal for Maintenance of High Energy Efficiency in Li–O2 Batteries

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Product

Resources

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Hierarchical Porous Carbon Spheres for High‐Performance Na–O₂ Batteries

Hierarchical Porous Carbon Spheres for High‐Performance Na–O₂ Batteries

Optimized Concentration of Redox Mediator and Surface Protection of Li Metal for Maintenance of High Energy Efficiency in Li–O₂ Batteries