Microelectrode Diagnostics of Lithium-Air Batteries

Gunasekara, Iromie; Mukerjee, Sanjeev; Plichta, Edward J.; Hendrickson, Mary; Abraham, K. M.

doi:10.1149/2.073403jes

Cited by 64 publications

(94 citation statements)

References 32 publications

(60 reference statements)

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“…When the potential range of the cathodic scan was extended more negative into 1.35 V, the intensity of a 2 diminished, and a new oxidation peak a 3 , attributed to Li 2 O oxidation (eq 7) by Laoire et al, became well distinct. The formation of Li 2 O at 2.21 V (as per eq 4) has been shown by using Raman after holding the electrode potential for 5 h. 11 The most distinguished difference between LiClO 4 and LiPF 6 was the oxidation observed above 4 V with a peak (peak a 4 ) attributed principally to oxidation of Li 2 CO 3 12,20 (discussed later with Raman results). The carbon-containing side product, Li 2 CO 3 , can be formed only by the reactions involving a carbon electrode and/or DMSO because the lithium salts do not contain carbon atoms.…”

Section: ■ Results and Discussionmentioning

confidence: 94%

“…Giving more confirmation, Gunasekara et al used Raman spectroscopy to prove the formation of Li 2 O 2 and Li 2 O on carbon in DMSO-based electrolyte by holding the electrode potential at the corresponding formation potentials of these oxides. 11 McCloskey et al 12 studied the Li−O 2 electrochemistry on carbon with LiN(CF 3 SO 2 ) 2 in DME by differential electrochemical mass spectroscopy. Only 2e − reduction of oxygen, resulting in peroxide, was found.…”

Section: ■ Introductionmentioning

confidence: 99%

“…15 Li 2 O was also at higher overpotentials (2.12 V). 11 Our work has an objective to study this point also.…”

Section: ■ Introductionmentioning

confidence: 99%

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Multiple Roles of Superoxide on Oxygen Reduction Reaction in Li⁺-Containing Nonaqueous Electrolyte: Contribution to the Formation of Oxide as Well as Peroxide

et al. 2015

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Oxygen reduction reaction (ORR) on carbon in lithium-ioncontaining nonaqueous electrolytes is supposed to follow a three-step mechanism: oxygen (O 2 0 ) to superoxide (O 2 − or LiO 2 ) to peroxide (O 2 2− or Li 2 O 2 ) to oxide (O 2− or Li 2 O). This work attempts to solve three controversial issues: (1) whether the superoxide is really formed; (2) whether the superoxide can be stable or immediately converts to peroxide; (3) whether the formation of oxide is feasible at the typical discharge potentials of lithium−air battery or the discharge product is only peroxide. ORR on carbon was studied in LiClO 4 or LiPF 6 containing dimethyl sulfoxide. The staircase cyclic voltammetry combined with Fourier transform electrochemical impedance spectroscopy (SCV-FTEIS) was used for the in situ investigation of ORR during potential scans. Oxygen was quasi-reversibly reduced to superoxide in the first step. Superoxide showed chemical stability in electrolyte. The superoxide was further reduced to surfaceadsorbed peroxide, and the reduction proceeded to produce oxide at higher overpotentials. We identified a novel chemical route resulting in oxide formation even at not-enough overpotentials: peroxide is reduced to oxide by superoxide as an in situ formed one-electron reducing agent. The electrolyte/electrode decomposition product, Li 2 CO 3 , was observed only in electrolyte with LiClO 4 .

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Section: ■ Results and Discussionmentioning

confidence: 94%

Section: ■ Introductionmentioning

confidence: 99%

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Multiple Roles of Superoxide on Oxygen Reduction Reaction in Li⁺-Containing Nonaqueous Electrolyte: Contribution to the Formation of Oxide as Well as Peroxide

et al. 2015

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“…Even at the very beginning of the cathodic sweep starting at about 2.5 V, we observed two oxidation products following the formation of one reduction product. From a detailed analysis of the CV results using 12 The Li 2 O 2 was identified from its characteristic Raman spectral absorption at ∼790 cm −1 of the product formed by electrolysis of O 2 on a carbon electrode in a DMSO/LiPF 6 solution at 2.32 V. The formation of Li 2 O was confirmed from the Raman spectrum of the product formed on the carbon electrode at 2.12 V. 12 The OER reactions shown in equation 5-7 are consistent with the sequential formation of the products in the anodic sweep following the incremental potential reversal steps associated with the cathodic CV scans. These ORR processes involving the initial formation of the one-electron reduction product LiO 2 in the non-aqueous Li-air cell using different solvent-based electrolytes is now recognized.…”

Section: Anodic (Oer) Reactionsmentioning

confidence: 99%

Electrolyte-Directed Reactions of the Oxygen Electrode in Lithium-Air Batteries

Abraham

2014

J. Electrochem. Soc.

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134

133

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Non-aqueous electrolytes play a prominent role in the redox reactions of the oxygen electrode in the non-aqueous Li-air battery. In all electrolytes the initial O 2 reduction reaction (ORR) product is superoxide, O 2 − , whose stability is determined by the Lewis acidity of the ion-pairing cations present in the medium as governed by the Hard Soft Acid Base (HSAB) theory. Our results suggest that depending on the basicity of the solvent as measured by its Donor Number (DN), the superoxide will be stabilized to varying lengths of time before transforming to O 2 2− via a chemical or an electrochemical reaction. Organic solvents decrease the Lewis acidity of Li + through the formation of solvates, Li + (solvent) n . As a result, high DN solvents such as dimethyl sulfoxide (DMSO), which decrease Li + acidity more than low DN solvents, provide longer life-time for the soft base O 2 − by forming the ion pair, Li + (DMSO) n -O 2 − . In low DN solvents such as 1, 2-dimethoxy ethane (DME) and tetraethyleneglycol dimethyl ether (TEGDME), the LiO 2 rapidly decomposes to the peroxide, Li 2 O 2 . As the ionic bond strength between the O 2 reduction product and the conducting salt cation becomes stronger, its rechargeability becomes poorer. Solvent electron donor property affects ORR catalysis also. There is intense world-wide research and development of a rechargeable lithium battery based on the Li/O 2 chemical couple, popularly known as the Li-air battery, encouraged by its very high theoretical specific energy (5200 Wh/kg) and low cost of the materials from which it can be fabricated.1,2 The theoretical specific energy of the Li-air battery is surpassed only by a battery based on the Li/F 2 couple.3 However, F 2, because of its high reactivity, is an impractical electrode material to construct batteries for powering consumer products such as cellphones, laptop computers, tablets, digital cameras, and electric vehicles. This leaves Li-air as the candidate of choice for an ultra-high energy density, low cost (air is free) rechargeable lithium battery. The Li-air battery is environmentally friendly as nontoxic electrolytes and other materials, besides Li and O 2, needed for fabricating it can be formulated. It is a safe battery despite having a Li metal anode because the cathode active material is not stored inside the battery cell.The Li-air battery is one of many metal-air batteries that could conceivably be fabricated (Table I).Among the various metal-O 2 couples, the Li-air is the most attractive battery since the cell discharge reaction involving metallic Li and oxygen to yield Li 2 O, according to the reaction 4Li + O 2 → 2Li 2 O, has an open circuit voltage of 2.91 V and a theoretical specific energy of 5200 Wh/kg (Table I). In practice, oxygen does not have to be stored in the battery which makes the theoretical specific energy excluding oxygen to be 11140 Wh/kg when the battery is initially fabricated. The battery weight will increase and its specific energy will decrease as it is discharged due to the accumulation ...

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“…Ideally, electrolytes for Li-air batteries should exhibit high ionic conductivity, resistance to decomposition, high oxygen solubility and fast oxygen diffusion rates. While many groups have focused on the degradation aspects and a few groups have investigated oxygen mass transport as a function of electrolyte chemistry, [4][5][6][7][8] fewer have deeply explored the impact of oxygen diffusion on cell performance (see Ref. 9 for a recent review of Li-air models).…”

mentioning

confidence: 99%

A Simple Model for Interpreting the Reaction–Diffusion Characteristics of Li-Air Batteries

Jones¹,

Gittleson²,

Templeton³

et al. 2017

J. Electrochem. Soc.

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With the goal of creating a model of a Li-air battery that is consistent with voltammetry data, we develop a full battery model capable of giving insight into details of cell operation otherwise inaccessible to common experimental techniques. With this model, we investigate the dependence of the current on: the diffusion characteristics of the electrolyte, the solubility of the ambient oxygen, the structure of the cathode, and aspects of the primary surface reaction. We explore modifications to a basic reaction-diffusion model of a full cell that bring better agreement with experimental data, including gas-electrolyte surface limited diffusion and a partially active cathode. We discuss how the basic form of the model and the simulated reaction and concentration profiles affect cell dynamics. Non-aqueous Li-air/Li-O 2 batteries have the highest theoretical energy density of any existing battery technology, 1-3 yet the practical application of these systems is hampered by electrolyte-related phenomena including material degradation and mass transport limited behavior. Ideally, electrolytes for Li-air batteries should exhibit high ionic conductivity, resistance to decomposition, high oxygen solubility and fast oxygen diffusion rates. While many groups have focused on the degradation aspects and a few groups have investigated oxygen mass transport as a function of electrolyte chemistry, 4-8 fewer have deeply explored the impact of oxygen diffusion on cell performance (see Ref. 9 for a recent review of Li-air models). Here we use a computational approach with experimental validation to model a full Li-air battery under transport-limited conditions and extract the influence of reaction-diffusion parameters.In designing Li-air battery systems voltammetry experiments play an important role in providing estimates of the reaction-diffusion properties which influence power density, energy density and cell lifetime. Voltammetry, a category of electroanalytic methods in which potential is varied linearly with time, has become a standard experimental tool to discern thermodynamics, kinetics and transport related to electrochemical processes. Randles and Sevcik derived a widely-used voltammetric correlation in which the peak current is proportional to the square root of the voltage scan rate for a reversible reaction at a flat electrode surface, 10-12 which was subsequently modified for semiirreversible electrochemical processes (e.g. oxygen reduction in Li-air batteries) by Delahay, 13,14 and Nicholson and Shain. 15,16 Despite the ability to estimate the diffusion coefficient with a simple algebraic equation, these semi-empirical correlations are inappropriate for application in devices with complex (i.e. porous) electrode geometries, as in Li-air batteries.Modeling electrochemical processes under practical device conditions, such as in a coin cell, provides insight into phenomena not easily accessible by experimentation. Generally speaking, a number of physical mechanisms are important in a complete battery model such as th...

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Microelectrode Diagnostics of Lithium-Air Batteries

Cited by 64 publications

References 32 publications

Multiple Roles of Superoxide on Oxygen Reduction Reaction in Li⁺-Containing Nonaqueous Electrolyte: Contribution to the Formation of Oxide as Well as Peroxide

Multiple Roles of Superoxide on Oxygen Reduction Reaction in Li⁺-Containing Nonaqueous Electrolyte: Contribution to the Formation of Oxide as Well as Peroxide

Electrolyte-Directed Reactions of the Oxygen Electrode in Lithium-Air Batteries

A Simple Model for Interpreting the Reaction–Diffusion Characteristics of Li-Air Batteries

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Microelectrode Diagnostics of Lithium-Air Batteries

Cited by 64 publications

References 32 publications

Multiple Roles of Superoxide on Oxygen Reduction Reaction in Li+-Containing Nonaqueous Electrolyte: Contribution to the Formation of Oxide as Well as Peroxide

Multiple Roles of Superoxide on Oxygen Reduction Reaction in Li+-Containing Nonaqueous Electrolyte: Contribution to the Formation of Oxide as Well as Peroxide

Electrolyte-Directed Reactions of the Oxygen Electrode in Lithium-Air Batteries

A Simple Model for Interpreting the Reaction–Diffusion Characteristics of Li-Air Batteries

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Multiple Roles of Superoxide on Oxygen Reduction Reaction in Li⁺-Containing Nonaqueous Electrolyte: Contribution to the Formation of Oxide as Well as Peroxide

Multiple Roles of Superoxide on Oxygen Reduction Reaction in Li⁺-Containing Nonaqueous Electrolyte: Contribution to the Formation of Oxide as Well as Peroxide