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Development of overpotentials during subsequent lithium plating/ stripping processes on the WE in Li/Li symmetrical cells with a Li reference electrode containing 1 M LiPF 6 in EC/DEC (3 : 7) as the electrolyte at j = 0.1 mA cm À2 .
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This comparative work studies the self-enforcing heterogeneity of lithium deposition and dissolution as the cause for dendrite formation on the lithium metal anode in various liquid organic solvent based electrolytes. In addition, the ongoing lithium corrosion, its rate and thus the passivating quality of the SEI are investigated in self-discharge...
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... potential of the lithium metal working electrode (WE) during constant current lithium deposition and dissolution in a Li/Li cell containing 1 M LiPF 6 in EC/DEC (3 : 7) electrolyte is presented in Fig. 1. The positive potentials of the Li WE against the Li/Li + reference electrode (RE) represent the overpotentials appearing during lithium dissolution, whereas the negative potentials represent the overpotentials during lithium deposi- tion on the WE. This experiment shows that the overpotentials of both the lithium deposition and ...
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... plating/stripping cycles is one order of magni- tude lower than the surface resistance of the cell measured directly after assembly (0 days) and two orders of magnitude lower than that measured after 6 days under OCP conditions. This effect correlates with the strong decrease of the over- potentials in the plating/stripping experiments (compare Fig. 1) and can be explained by a large increase in the surface area of the lithium anode during cycling. The different shapes of the impedance spectra are coherent with the changing lithium electrode surface morphology and the chemically different SEI after 50 and 370 ...
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... the overpotential (E). However, when the experiment starts with a lithium dissolution process as in the plating/stripping experiments with Li/Cu cells (compare Fig. 3 with the 1st cycle of Fig. 4), only the electrode behaviour indicated by the regions D and E is observed. The experiments with changing charge capacities of the Li WE (compare with Fig. 11a and b) indicate that the capacity of the preceding lithium deposition process correlates with the duration of the first region (C) of the following lithium dissolution ...
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... after a rest time of 24 h or 120 h. The comparison of the Coulombic efficiency of this lithium deposition and dissolution cycle with deposition and dissolution cycles without a rest time shows how much active lithium is 'lost' during the rest time. The higher the loss of lithium in the rest time, the lower is the passivation quality of the SEI. Fig. 10a presents the development of the charge capacity of the WE and the Coulombic efficiency of subsequent lithium deposition/dissolution on the Cu CE in 1 M LiPF 6 in EC/DEC (3 : 7) electrolyte. The Coulombic efficiency increases during the first cycles, which indicates the formation of a passivating film on the deposited ...
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... the overpotential profiles of the cycles before and after the rest time (Fig. 11a) indicate that the following 12th cycle only differs in the lithium dissolution process at the WE. This is due to the lower amount of lithium deposited on the WE after the rest time in the 11th ...
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... Fig. 10a it can also be seen that the Coulombic efficiency drops from 87% to 0% between the 10th cycle and the 11th cycle, which includes 5 days of rest time (Table 3). This indicates a complete corrosion of the deposited lithium on the Cu CE during the rest time. The following 12th cycle shows a Coulombic efficiency of 60% and it takes another ...
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... cycle, which includes 5 days of rest time (Table 3). This indicates a complete corrosion of the deposited lithium on the Cu CE during the rest time. The following 12th cycle shows a Coulombic efficiency of 60% and it takes another 8 cycles to reach 87%. As the Coulombic efficiencies and thus the over- potential profiles of lithium dissolution (Fig. 11b) after the self- discharge cycle are also similar to those of the SEI formation in the first cycles of the experiment (compare Fig. 4), it can be deduced that in contrast to the experiment with a rest time of 24 h the passivating film on the Cu foil is now lost during the rest time and has to be formed again. 6 in EC/DEC (3 : 7), 1 M ...
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... 43-51% 43-54% 53% 12% (À30%) - DMSO 20-33% 28-63% 55-82% 0% (À33%) - Analogous to the experiments in the EC/DEC-based electro- lyte, the passivating properties of the surface film formed by the other electrolytes were investigated (Table 3). These experi- ments were carried out at j = 0.1 mA cm À2 for 1 M LiPF 6 in EC/DMC (1 : 1) electrolyte (Fig. 10b) and at j = 0.01 mA cm À2 for 1 M LiPF 6 in TEGDME and 1 M LiTFSI in DMSO electrolytes. Also in these electrolytes it can be observed that the Coulombic efficiencies increase continuously to a certain plateau during the first cycles. It can be concluded that the electrolyte decom- position compounds of these electrolytes also form a ...
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... was measured using a Solartron SI 1287 potentiostat in combination with a Solartron SI 1260 impedance/gain phase analyser. The spectra were detected between 1 mHz and 1 MHz with an amplitude of 5 mV. They were analysed using ZView Ver. 3.2b of Scribner Ass. Inc., and were interpreted by the equivalent circuit in Fig. 12. R1 corresponds to the Ohmic resistance of the electrolyte R electrolyte . The sum of R2 and R3 refers to the semicircle shown in the Nyquist plots, which was interpreted as the 'Li electrode surface resistance' (R surface = R2 + R3) of both ...
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The effect of electrolyte salt on the solid electrolyte interphase (SEI) is discussed with respect to improvement of the lithium metal anode. Lithium bis(fluorosulfonyl)imide (LiFSI) and lithium nitrate (LiNO3) were dissolved together in dimethyl sulfoxide (DMSO), in which the ratios of LiNO 3 :LiFSI (x:100-x mol%) were in the range of 0<x<100. Ele...
Citations
... However, several fundamental challenges need to be addressed for the stable and safe operation of lithium metal batteries. With organic liquid electrolyte, repeated charging and discharging results in severe volume changes of lithium which leads to the rupture of solid electrolyte interphase (SEI), uncontrolled lithium dendrite growth and ultimately short circuit [8,9]. In addition, high reactivity of lithium metal with liquid electrolyte causes unwanted side reactions leading to lower Coulombic efficiency due to the loss of lithium inventory and even thermal runaway under extreme circumstances [10,11]. ...
The development of next-generation batteries, utilizing electrodes with high capacities and power densities requires a comprehensive understanding and precise control of material interfaces and architectures. Electro-chemo-mechanics plays an integral role in the morphological evolution and stability of such complex interfaces. Volume changes in electrode materials and the chemical interaction of electrode/electrolyte interfaces result in non-uniform stress fields and structurally-different interphases, fundamentally affecting the underlying transport and reaction kinetics. The origin of this mechanistic coupling and its implications on degradation is uniquely dependent on the interface characteristics. In this review, the distinct nature of chemo-mechanical coupling and failure mechanisms at solid-liquid interfaces and solid-solid interfaces is analyzed. For lithium metal electrodes, the critical role of surface/microstructural heterogeneities on the solid electrolyte interphase (SEI) stability and dendrite growth in liquid electrolytes, and on the onset of contact loss and filament penetration with solid electrolytes (SEs) is summarized. With respect to composite electrodes, key differences in the microstructure-coupled electro-chemo-mechanical attributes of intercalation- and conversion-based chemistries are delineated. Moving from liquid to solid electrolytes in such cathodes, we highlight the significant impact of solid-solid point contacts on transport/mechanical response, electrochemical performance, and failure modes such as particle cracking and delamination. Lastly, we present our perspective on future research directions and opportunities to address the underlying electro-chemo-mechanical challenges for enabling next-generation lithium metal batteries.
... Iron has similar properties to other metal ion batteries. The additional advantage of RIIBs is the significantly lower chances of forming dendrites, which cause short-circuiting, a critical issue in LIBs [31]. The redox potential of iron is very high (− 0.44 V vs. standard Ionics hydrogen electrode (SHE)) than lithium-ion (− 3.04 V vs. SHE). ...
We fabricated rechargeable iron ion batteries (RIIBs) using mild steel (MS) as a negative electrode, vanadium penta oxide as a positive electrode, and ferrous perchlorate hydrate in tetra-ethylene glycol dimethyl ether (TGDME)-based solvent under ambient conditions without any inert atmosphere and investigated the performance degradation. The cell exhibits ~ 120 mAh g⁻¹ specific capacity at a 33 mAg⁻¹ current density. The initial capacity fades to about 41% in 30 cycles. The cell was disassembled, and post-mortem characterizations were carried out for both electrodes. The performance degradation is attributed to the corrosion of the mild steel and the formation of multiphase iron–vanadium-based oxides at the cathode end, reducing the iron ion concentration. Thus, the present studies provide a microscopic understanding of capacity fading in iron ion batteries and may assist in designing suitable electrode materials for the improved electrochemical response.
... Specifically, the overpotential profile grows gradually as lithium becomes more difficult to strip with the maximum overpotential associated with the bulk lithium electrode. In some cases, the overpotential decreases after the maximum overpotential due to the beginning of the pitting process, which induces preferential stripping from pitted areas, leading to more porous and roughened deposits [34]. ...
Lithium metal batteries are considered a promising technology to implement high energy density rechargeable systems beyond lithium-ion batteries. However, the development of dendritic morphology is the basis of safety and performance issues and represents the main limiting factor for using lithium anodes in commercial rechargeable batteries. In this study, the electrochemical behaviour of Li metal has been investigated in organic carbonate-based electrolytes by electrochemical impedance spectroscopy measurements and deposition/stripping galvanostatic cycling. Low amounts of tetraalkylammonium hexafluorophosphate salts have been added to the electrolytes with the aim of regulating the lithium deposition/stripping process through the electrostatic shielding effect that improves the lithium deposition. The use of NH4PF6 also determined good lithium deposition/stripping performance due to the chemical modification of the native solid electrolyte interphase via direct reaction with lithium.
... Over time SEI growth and thickening leads to LLI and capacity loss 17 . The continuous volume changes of the graphite particles during cycling strongly stress the limitedly flexible SEI layer 18,19 , hence a repetitive fracture of the already formed nanometer-thick film could happen, with a further exposition of the underlying surfaces 20 . We include this mechanism using an SEI formation rate law depending on SOC-dependent stress on the SEI 8 . ...
This article presents the development, parameterization, and experimental validation of a pseudo-three-dimensional multiphysics aging model of a 500 mAh high-energy lithium-ion cell with graphite anode and NMC cathode. This model includes electrochemical reactions for SEI formation at the graphite anode, lithium plating, and SEI formation on plated lithium. The thermodynamics of the aging reactions are modeled depending on temperature and ion concentration and the kinetics are described with an Arrhenius-type rate law. Good agreement of model predictions with galvanostatic charge/discharge measurements and electrochemical impedance spectroscopy is observed over a wide range of operating conditions. The model allows quantification of capacity loss due to cycling near beginning-of-life and visualization of aging colormaps as a function of operating conditions. The model predictions are also qualitatively verified through voltage relaxation, cell expansion, and cell cycling measurements. Based on this full model, six different aging indicators for determination of the limits of fast charging are derived from post-processing simulations of a reduced pseudo-two-dimensional isothermal model without aging mechanisms. The most successful indicator is based on combined plating and SEI kinetics calculated from battery states available in the reduced model. This methodology is applicable to standard pseudo-two-dimensional models available both commercially and as open source.
... Building an SEI at the initial stage passivates the electrode surface at a large negative potential and prevents further electrolyte decomposition during prolonged cycling. [3,[17][18][19] In contrast to intercalationbased graphite anodes, the SEI formed at the LMA surface cannot tolerate large volume changes, ultimately leading to a structural collapse during the Li plating/stripping cycles. [3,20,21] Such passivation failure allows electrolyte penetration and excessive accumulation of electrolyte-consuming SEI, resulting in a significant buildup of porous, insulating passivation (the reacted Li) layers, which can increase the cell's impedance and eventually terminate its operation. ...
Despite the promises in high‐energy‐density batteries, Li‐metal anodes (LMAs) have suffered from extensive electrolyte decomposition and unlimited volume expansion owing to thick, porous layer buildup during cycling. It mainly originates from a ceaseless reiteration of the formation and collapse of solid‐electrolyte interphase (SEI). This study reveals the structural and chemical evolutions of the reacted Li layer after different cycles and investigates its detrimental effects on the cycling stability under practical conditions. Instead of the immediately deactivated top surface of the reacted Li layer, the chemical nature underneath the reacted Li layer can be an important indicator of the electrolyte compositional changes. It is found that cycling of LMAs with a lean electrolyte (≈3 g Ah−1) causes fast depletion of salt anions, leading to the dynamic evolution of the reacted Li layer structure and composition. Increasing the salt‐solvent complex while reducing the non‐solvating diluent retards the rate of depletion in a localized high‐concentration electrolyte, thereby demonstrating prolonged cycling of Li||NMC622 cells without compromising the Li Coulombic efficiencies and high‐voltage stability. Looking underneath the reacted Li layer reveals its structural and chemical evolutions. Contrary to the flooded electrolyte, the reacted Li layer developed at lean electrolyte suffers from incremental deterioration and engenders the cycling history as an important indicator of electrolyte compositional changes, delivering a clue for electrolyte design principle for stable cycling of Li‐metal batteries under stringent conditions.
... The variation in voltage during cell cycling has been often used to gain insight into the mechanisms behind Li nucleation, dissolution, and deposition 74,78,166,170 . ...
... Also, in accordance with the previous experiment results78 , the shape of the potential profile of the counter electrode changes during the second plating process in a manner that is highly similar to that of the coin cell(Figure 2-6, supporting information). As previously reported166,170 , the first plateau corresponds to the stripping of Li from the pre-existing mossy dendrites on the surface of the Li. After no lithium is left to be extracted from the dendritic surface, the overpotential starts to increase due to the Li stripping from the bulk Li anode electrode166 . ...
... Besides, the modification of the counter electrode's potential in the second part of the second plating process is responsible for the drastic change in the cell potential(Figure 2-3f). As mentioned in the introduction and already widely reported in the literature, this effect can be correlated to the incomplete stripping of the previously plated dendrites at the counter electrode, and the inset of lithium stripping from the bulk of the lithium counter electrode78,166,170 . Based on these observations, to ensure a more accurate interpretation of the data, we recommend the use of a three-electrode configuration58,169 to correctly evaluate the nucleation overpotential of the Li metal system, or at least to focus on the second plating process (or the following ones) in the case of the use of a two-electrode cell. ...
Lithium-ion batteries (LIBs) have been leading the power storage market since the 1990s, yet they cannot satisfy humankind's exponential increase in energy demand. Therefore, recently, lithium metal batteries (LMBs) have been resurrected with the expectation to offer higher capacity and energy density than the current LIBs. However, some major issues, such as huge volume change and continuous dendrite formation, have to be tackled to commercialize LMBs. This thesis aims at providing an in-depth insight into lithium deposition during the early stages of its nucleation and growth, as well as the impact of experimental parameters on the electrochemical performance of LMBs. The work has been carried out in collaboration between ICGM and Uppsala University, and financed by the Alistore-ERI network. A thin layer of zinc oxide (ZnO) was deposited on nickel foam with the atomic layer deposition process in order to evaluate the performance and behavior of lithium plating/stripping. This modification resulted in better electrochemical performance due to the different lithium morphologies formed during the plating/stripping cycles, which were thoroughly investigated using SEM and EDS combined with DFT calculations. Further, we examined the origin of phenomena that affected electrochemical performance and attempted to identify a correlation between them. The nucleation overpotential was found to originate from the lithium extraction of the counter electrode instead of from the nuclei formation on the working one. Finally, several parameters affecting Coulombic efficiency (CE) were studied, including stripping cutoff voltage, electrolyte quantity, pre-cycled SEI formation, and electrode surface modification. Overall, this thesis contributes to the design of better experiments for future LMB studies and a deeper understanding of the mechanism of cell failure in lithium anode.
... The potential response of the symmetric cells with the configuration of Li|PMHP2|Li and Li/Celgard/Li was erected in Fig. 7d. The initial overpotential www.nature.com/scientificreports/ of the battery cell with PMHP2 membrane was between − 150 and 150 mV due to a starting point of lithium dissolution and deposition processes at the beginning that had its impact on the potential response, which in further cycles declined and stabilized at − 20 to 20 mV proving that the kinetic of lithium mobility was balanced 53 . The durability of the membrane was clearly seen from its 1000 h of performing duration with high current density. ...
A novel crosslinked electrospun nanofibrous membrane with maleated lignin (ML) and poly(acrylonitrile) (PAN) is presented as a separator for lithium-ion batteries (LIBs). Alkali lignin was treated with an esterification agent of maleic anhydride, resulting in a substantial hydroxyl group conversion to enhance the reactivity and mechanical properties of the final nanofiber membranes. The maleated lignin (ML) was subsequently mixed with UV-curable formulations (up to 30% wt) containing polyethylene glycol diacrylate (PEGDA), hydrolyzed 3-(Trimethoxysilyl)propyl methacrylate (HMEMO) as crosslinkers, and poly(acrylonitrile) (PAN) as a precursor polymer. UV-electrospinning was used to fabricate PAN/ML/HMEMO/PEGDA (PMHP) crosslinked membranes. PMHP membranes made of electrospun nanofibers feature a three-dimensional (3D) porous structure with interconnected voids between the fibers. The mechanical strength of PMHP membranes with a thickness of 25 µm was enhanced by the variation of the cross-linkable formulations. The cell assembled with PMHP2 membrane (20 wt% of ML) showed the maximum ionic conductivity value of 2.79*10⁻³ S cm⁻¹, which is significantly higher than that of the same cell with the liquid electrolyte and commercial Celgard 2400 (6.5*10⁻⁴ S cm⁻¹). The enhanced LIB efficiency with PMHP2 membrane can be attributed to its high porosity, which allows better electrolyte uptake and demonstrates higher ionic conductivity. As a result, the cell assembled with LiFePO4 cathode, Li metal anode, and PMHP2 membrane had a high initial discharge specific capacity of 147 mAh g⁻¹ at 0.1 C and exhibited outstanding rate performance. Also, it effectively limits the formation of Li dendrites over 1000 h. PMHP separators have improved chemical and physical properties, including porosity, thermal, mechanical, and electrochemical characteristics, compared with the commercial ones.
... Electrochemical Impedance Spectroscopy (EIS) is a powerful characterization technique consisting of the application of a sinusoidal current signal and measuring the voltage response of the cell at different frequencies to compute the impedance [35,[48][49][50][51][52][53]. Therefore, in BMS applications, a dedicated hardware is required for its application. ...
... As observed in [35], EIS spectra throughout cycling are affected by Loss of Lithium Inventory (LLI), that is the consumption of lithium ions by parasitic reaction (SEI growth) and decomposition reactions of the SEI or the electrolyte and LAM processes. EIS has been applied to LMBs [50], showing a large rise of the mid-frequency arch in both real and imaginary impedances and an increase of the ohmic resistance. Impedance evolution during cell aging can be tracked by fitting the curve with Equivalent Circuit Models (ECMs) and by tracking the impedance value of specific parameters (e.g., the maximum of the arch, the width of the arch and the minimum before the tail) [54,55]. ...
The application of Lithium Metal Batteries (LMBs) as secondary cells is still limited due to dendrite degradation mechanisms arising with cycling and responsible for safety risk and early cell failure. Studies to prevent and suppress dendritic growth using state-of-the-art materials are in continuous development. Specific detection techniques can be applied to verify the internal condition of new LMB chemistries through cycling tests. In this work, six non-invasive and BMS-triggerable detection techniques are investigated to anticipate LMB failures and to lay the basis for innovative self-healing mechanisms. The novel methodology is based on: (i) defining detection parameters to track the evolution of cell aging, (ii) defining a detection algorithm and applying it to cycling data, and (iii) validating the algorithm in its capability to detect failure. The proposed methodology is applied to Li||NMC pouch cells. The main outcomes of the work include the characterization results of the tested LMBs under different cycling conditions, the detection techniques performance evaluation, and a sensitivity analysis to identify the most performing parameter and its activation threshold.
... The GPE showed an increased overpotential during the first 60 cycles, attributable to the formation of a pseudo-SEI layer on the Na surface. [55] After ca. 100 cycles, the GPE showed a reduced and stable overpotential up to the 450 th cycle, resulting from the breakage of the pseudo-SEI layer during cycling and the successful formation of a stable SEI layer. The pseudo-SEI formation on the Na anode in the GPE is likely to occur via the polymerization of PETA by Na during cell fabrication. ...
High‐temperature sodium‐sulfur battery (HT Na–S) technology has attracted substantial interest in the stationary energy storage sector due to its low cost and high energy density. However, the currently used solid electrolyte (ß‐alumina) is expensive and can only be operated at high temperatures, which compromises safety. On the other hand, liquid electrolytes in room temperature sodium‐sulfur batteries (RT Na–S) are susceptible to dendrite formation and polysulfide shuttle. Consequently, an electrolyte with both solid (shuttle blocking) and liquid (ionic conductivity) properties to overcome the above‐mentioned issues is highly desired. Herein, a high‐performance quasi‐solid state crosslinked gel polymer electrolyte (GPE) prepared in situ using pentaerythritol triacrylate (PETA) exhibiting high ionic conductivity of 2.33 mS cm⁻¹ at 25 °C is presented. The GPE‐based electrolyte shows high stability resulting in a high discharge capacity of >600 mAh gs⁻¹ after 2500 cycles with an average Coulombic efficiency of 99.91%. Density functional theory calculations reveal a weak interaction between the Na⁺ ions and the oxygen molecules of the PETA moiety, which leads to a facile cation movement. The crosslinked polymer network is tightly connected to the cathode and can confine sulfides, thereby facilitating the conversion process.
... where overpotentials were averaged from the voltage plateaus during plating. Samples in Ar, while initially cycling with a low overpotential, showed a large jump in polarization after the first 9 cycles, indicating that no more lithium could be removed from the Cu electrode [128,129]. Almost 40% irreversible loss in capacity occurred in a single plating/stripping cycle, Figure 4.2.1d. This poor performance in agreement with previous studies using ether electrolytes [130]. ...
Lithium air batteries (LABs) promise extremely high gravimetric energy densities. Similar to fuel cells, mass transport of redox active species, such as dissolved oxygen gas or redox mediators, is one of the challenges faced by LABs. While increasing mass transport increases LAB cell performance, it can also increase crossover of the redox active species from one electrode to the other, resulting in capacity loss and interfacial reactions. The interplay between mass transport and crossover of redox active species from one electrode has not been extensively discussed in literature and requires detailed characterization. In this work, mass transport effects and crossover rates were characterized using magnetic resonance methodologies, electrochemical techniques, and computational modelling. The crossover reactions that arise when redox active species migrate to the Li metal anode and how they affect the solid-electrolyte interphase (SEI) were then studied. Nuclear magnetic resonance (NMR) spectroscopy was used to measure oxygen mass transport in LABs in Chapter 3, capitalizing on the paramagnetic properties of O2. This method has not been previously used to measure O2 in LAB electrolytes and provides direct experimental evidence of the O2 coordination environment predicted by previous computational studies. The dissolved O2 were quantified during LAB operation using the NMR methodology. In addition, an increase in discharge capacity and decrease in overpotentials was observed when increasing O2 mass transport, both in LAB Swagelok and flow cells. Computational modelling supports these observations and suggests improved electrode utilization when O2 mass transport is improved. However, crossover of the dissolved oxygen was also observed in both computational and experimental studies, whereby O2 diffuses from the gas electrode over to the anode. Due to the reactivity of Li metal, the crossover of O2 changes both the SEI composition as well as the Li metal deposition morphologies as discussed in Chapter 4. Redox mediators are soluble catalysts employed to decrease overpotentials in LABs and promote solution-phase reactions. The mass transport and crossover of redox mediators in LABs were then studied in Chapter 5, focusing on reactions of TEMPO (2,2,6,6-tetramethylpiperidinyloxyl), which is a redox mediator used on charge. Due to its paramagnetic properties, operando magnetic resonance and computational methods were used, similar to the previous chapters studying dissolved O2. Again, an improvement in overpotentials when increasing the mass transport was observed while at the same time increasing the crossover and redox shuttling reactions. The reactions of TEMPO with the Li metal SEI were subsequently characterized in Chapter 6 with the aim of both understanding possible degradation reactions and using TEMPO as a probe to measure SEI properties. This thesis concludes with outlooks on methods to limit crossover reactions, engineering the Li metal SEI, and new methods to characterize the SEI.
