Potassium Oxygen Batteries Research Articles

Hierarchical Porosity and Surface Oxygenation of Carbon-Based Cathodes Enhances Discharge Capacity and Decreases Discharge Overpotential of Potassium–Oxygen Batteries

Hierarchical Porosity and Surface Oxygenation of Carbon-Based Cathodes Enhances Discharge Capacity and Decreases Discharge Overpotential of Potassium–Oxygen Batteries

Hybrid-Solvent Electrolytes for Enhanced Potassium-Oxygen Battery Performance.

Rechargeable potassium-oxygen batteries (KOB) are promising next-generation energy storage devices because of the highly reversible O2/O2- redox reactions during battery charge and discharge. However, the complicated cathode reaction processes seriously jeopardize the battery reaction kinetics and discharge capacity. Herein, we propose a hybrid-solvent strategy to effectively tune the K+ solvation structure, which demonstrates a critical influence on the charge-transfer kinetics and cathode reaction mechanism. The cosolvation of K+ by 1,2-dimethoxyethane (DME) and dimethyl sulfoxide (DMSO) could greatly decrease overpotentials for the cathode processes and increase the cathode discharge capacity. Furthermore, the Coulombic efficiency for the cathode could be significantly improved with the enhanced solution-mediated KO2 growth and stripping during cycling. This work provides a promising electrolyte design approach to improve the electrochemical performance of the KOB.

The effects of oxygen pressure on the discharge performance of potassium–oxygen batteries

Applying high oxygen pressure drastically improves the discharge performance of potassium-oxygen batteries. High oxygen pressure can also prevent parasitic reactions leading towards K2SO4 and K2CO3 induced by oxygen depletion within the cathode.

A stable structure zinc manganese oxide (ZnMn2O4) synthesized via a facile coprecipitation method as high performance air electrode catalyst for potassium-oxide batteries

Potassium-oxygen batteries as promising energy storage system have been widely concerned at present. In this paper, we obtain a zinc manganese oxide (ZnMn2O4) catalyst via a facile coprecipitation method. XRD and Raman tests show that ZnMn2O4 at the Zn and Mn molar ratio to 1:2 along with hot-heat treatment at 150 °C has a higher crystallinity and lower heterophase content. SEM observes that ZnMn2O4 material shows uniform spherical morphology with loose arrangement, which can be beneficial to mass transfer and discharge products storage. Electrochemical test results display that air electrode with ZnMn2O4 as catalyst has rapid electron and ion transfer speed and successfully carries out the charge and discharge process in the potassium-oxygen battery system.

Status of rechargeable potassium batteries

Future renewable energy integrated grid systems require rechargeable batteries with low cost, high safety, and long cycle life. The much higher abundance of sodium and potassium compared to lithium in earth crust indicates that rechargeable sodium and potassium batteries are attractive replacements for lithium-ion batteries. Rechargeable potassium batteries have gained tremendous attention during the past decade. However, the development of rechargeable potassium batteries is still in its infancy. This review summarizes the recent technological developments in rechargeable potassium batteries. First, we summarize the latest achievements of active materials design, mechanistic understanding, and exploration of new active materials. We propose new directions in tuning the architecture and enhancing the electrochemical performances of high-performance anodes and cathodes. Second, we also summarize the advances that have been achieved in the new configurations of rechargeable potassium battery systems (potassium-ion capacitors, potassium dual ion batteries, potassium-sulfur batteries, and potassium-oxygen batteries). Finally, we propose future directions and design strategies that could be employed to advance rechargeable potassium batteries toward commercial applications. In this review, a large family of rechargeable batteries based on potassium as charge carrier are summarized. Rechargeable potassium ion batteries include potassium-ion batteries, potassium-ion capacitors, potassium-ion-based dual ion batteries, potassium-sulfur batteries, and potassium-oxygen batteries. Future directions and design strategies that could be employed to advance rechargeable potassium batteries toward commercial applications are proposed. • Rechargeable potassium ion battery as a promising rechargeable battery system. • Current status and future research trends of rechargeable potassium batteries. • Strategies for developing practical anodes and cathodes for potassium batteries. • Recent advances of different configurations of rechargeable potassium batteries.

In Situ probing of solid/liquid interfaces of potassium–oxygen batteries via ambient pressure X-ray photoelectron spectroscopy: New reaction pathways and root cause of battery degradation

Direct probing of metal–oxygen chemistry at the solid/liquid interface is essential to unravel the reaction mechanism of metal–air batteries. Ambient pressure X-ray photoelectron spectroscopy (APXPS) is an effective tool to study metal–oxygen reactions but has been limited to solid-state environments. Here, for the first time, we demonstrate in situ probing of potassium oxygen reduction/evolution reaction (ORR/OER) via APXPS in ionic liquid-based air batteries. We reveal the formation and oxidation of K2O and K2O2 in K–O2 batteries, highlighting new reaction pathways in addition to the widely established one-electron process in K–O2 batteries. Importantly, we show that the formation and subsequent oxidation of K2O2 trigger irreversible cell chemistry, which could be responsible for capacity decay in K–O2 batteries. We further show that common impurities in air such as H2O and CO2 reduce chemical reversibility of ORR and OER. This study reveals root causes of irreversible cell chemistry in K–air batteries via direct probing of ionic liquid-based air batteries via APXPS, which can be widely applied to study the chemistry of solid/liquid interfaces of metal–air batteries.

Potassium-Oxygen Batteries: Significance, Challenges, and Prospects.

To mitigate a global crisis of Li depletion, potassium-based rechargeable batteries have received significant attention because of their low cost and high specific energy density. In particular, the rechargeable potassium oxygen (K-O2) battery has been recognized as a promising energy storage technology because of its low overpotential and high round-trip efficiency based on the single-electron redox chemistry of potassium superoxide. Despite these merits, research on the development of K-O2 batteries is still in its early stages owing to a lack of understanding of the fundamental reaction chemistry and the difficulties encountered in handling, in terms of practical acceptability. Hence, it is necessary to summarize the representative works and provide overall insights on K-O2 batteries and recommendations for future studies. In this Perspective, we critically review the important scientific aspects of K-O2 batteries, discuss the current challenges encountered, and provide recommendations from the scientific and practical points of view. We hope that this Perspecitve will be helpful in designing innovative and advanced K-O2 batteries.

Pursuing graphite-based K-ion O2 batteries: a lesson from Li-ion batteries

An artificial SEI enables reversible graphite-intercalation in a potassium bis(trifluoromethanesulfonyl)imide (KTFSI)-based electrolyte to ensure the holistic anode–electrolyte–cathode compatibility in the potassium-ion oxygen battery.

On the importance of ion pair formation and the effect of water in potassium–oxygen batteries

Oxygen reduction in the presence of potassium ions has been identified as a promising candidate for the cathode reaction in aprotic metal–air batteries due to its inherent reversibility. Here, we explore the kinetics of the oxygen reduction reaction in a dimethyl sulfoxide-based electrolyte using rotating ring-disk electrode measurements as well as differential electrochemical mass spectrometry. Thorough kinetic analysis reveals that the oxygen reduction in presence of K+ behaves like an ideal model system and that the usual relationships for reversible reactions are applicable. From the comparison of different electrode materials it has been concluded that the electrode material has an influence on the kinetics of the reduction of oxygen to superoxide, which challenges the picture of a simple outer-sphere mechanism. In fact, the reduction of oxygen to superoxide is most facile at glassy carbon electrodes, whereas it is significantly lower at gold electrodes. Rate constants are reported for gold, platinum and glassy carbon. Adding potassium perchlorate to an inert, tetrabutylammonium-containing electrolyte showed a significant stabilization of the superoxide via a shift of the half-wave potentials of the reduction to more positive potentials. This stabilization of superoxide by potassium as compared to tetrabutylammonium shows that the current interpretation of the cation's effect via Pearson's acid-base (HSAB) concept has to be used with great caution. From a detailed analysis of the effect of K+, the equilibrium constant of ion-pairing between superoxide and K+ has been determined as 725 L mol−1. Using isotopically labelled H218O it has been shown that the formation of potassium peroxide is alleviated in the presence which is attributed to a further reaction of the peroxide with water. This in contrast to Li+-containing electrolytes, where water has the opposite effect and prevents peroxide formation. Finally, the unexpected consumption of oxygen has been observed during the oxidation of species deposited onto the surface of the electrode, which has been correlated to the amount of CO2 evolution.

Binder Degradation in Sodium- and Potassium-Oxygen Batteries

Non-aqueous sodium- and potassium-oxygen batteries (Na/K-O2) are promising candidates for alternative energy storage based on higher theoretical specific energy over conventional lithium-ion batteries1-2. The cell operation following the one electron reduction/oxidation of the metal superoxide (NaO2 and KO2) allows low charge polarisation and high columbic efficiency, which are some of the main challenges in the lithium-oxygen (Li-O2) counterpart. However, parasitic reactions between cell components and metal superoxides are still to be fully investigated and better understood. The present work accomplished a study of the electrochemical performance and characterised the discharge products in ether-based cells operating with porous carbon cathodes cast with different polymeric binders. When utilising poly(tetrafluoroethylene) (PTFE) and carboxymethylcellulose sodium (CMC), superoxide was detected via Raman spectroscopy as the main reaction product in both sodium and potassium systems. Poly(vinylidene fluoride) (PVDF), which is known to be unstable in the chemical environment of metal-oxygen cells3, was found to only affect the discharge/charge potential profile and reaction mechanism of Na-O2 cells but not K-O2. This is the result of a negative synergistic effect between PVDF dehydrofluorination reaction and the NaO2 dissolution/ionisation, which increases the formation of hydroperoxyl radical (HO2). HO2 is an intermediate reactive species in the oxidative decomposition reaction of the ether electrolyte. The formation of sodium carbonate and sodium formate results as parasitic products that are only oxidised at large overpotential, as detected via FTIR analysis. In K-O2 cells utilising PVDF binder, the desired reaction product formation is confirmed via XRD and SEM/EDS analysis, despite the detection of identical PVDF decomposition via Raman spectroscopy. As such, we will highlight how interplay of all cell components drives the overall reversibility of the desired oxygen electrochemistry in metal-air cells. References Adelhelm, P.; Hartmann, P.; Bender, C. L.; Busche, M.; Eufinger, C.; Janek, J., From lithium to sodium: cell chemistry of room temperature sodium–air and sodium–sulfur batteries. Beilstein journal of nanotechnology 2015, 6 (1), 1016-1055.Xiao, N.; Ren, X.; McCulloch, W. D.; Gourdin, G.; Wu, Y., Potassium Superoxide: A Unique Alternative for Metal–Air Batteries. Accounts of chemical research 2018, 51 (9), 2335-2343.Black, R.; Oh, S. H.; Lee, J.-H.; Yim, T.; Adams, B.; Nazar, L. F., Screening for superoxide reactivity in Li-O2 batteries: effect on Li2O2/LiOH crystallization. Journal of the American Chemical Society 2012, 134 (6), 2902-2905. Figure 1

Frontispiece: Alkali-Oxygen Batteries Based on Reversible Superoxide Chemistry

Rechargeable superoxide batteries have the potential to surpass current lithium-ion technology due to their high theoretical energy densities. The use of superoxides as an energy storage material is highly advantageous when compared to their close relatives, peroxides. The two most studied systems are sodium and potassium-oxygen batteries. Both batteries present unique advantages and challenges. For more information, see the Minireview by Y. Wu et al. on page 17627 ff.

Alkali-Oxygen Batteries Based on Reversible Superoxide Chemistry.

Rechargeable superoxide (O2 - ) batteries have the potential to surpass current lithium-ion technology due to their high theoretical energy densities. The use of superoxides as an energy storage material is highly advantageous when compared to their close relatives, peroxides. This is due to enhanced reversibility of the 1-electron redox process. To efficiently stabilize superoxides, larger metal cations are required such as sodium and potassium. Therefore, the two most studied systems are sodium and potassium-oxygen batteries. Both batteries present unique advantages and challenges. In this minireview, we summarize the current research for each superoxide-based battery and offer perspective for further research.

Recent Progress in Rechargeable Potassium Batteries

AbstractThe topic of sustainable and eco‐friendly energy storage technologies is an issue of global significance. To date, this heavy burden is solely addressed by lithium‐ion battery technology. However, the ongoing depletion of limited global lithium resources has restricted their future availability for Li‐ion battery technology, and hence, a significant price increase is expected. This grim situation is the driving force for the development of the “beyond Li‐ion battery” strategy involving alternatives that have several advantages over conventional Li‐ion batteries in terms of cost, durability, safety, and sustainability. Potassium, the closest neighboring alkali element after sodium, offers some unique advantages over lithium and sodium as a charge carrier in rechargeable batteries. Potassium intercalation chemistry in potassium‐ion batteries (KIBs) is successfully demonstrated to be compatible with Li‐ion batteries and sodium‐ion batteries. In addition to KIBs, potassium–sulfur and potassium–oxygen batteries have emerged as new energy‐storage systems due to their low costs and high specific energy densities. This review covers the key technological developments and scientific challenges for a broad range of rechargeable potassium batteries, while also providing valuable insight into the scientific and practical issues concerning the development of potassium‐based rechargeable batteries.

Dimethyl Sulfoxide-Based Electrolytes for High-Current Potassium–Oxygen Batteries

The thermodynamic stability and relatively low free energy of formation (ΔG0 = −239.4 kJ mol–1) of KO2 offer the possibility of K–O2 cells as a catalyst-free, low overpotential energy storage syste...

Superoxide Stabilization and a Universal KO2 Growth Mechanism in Potassium-Oxygen Batteries.

Rechargeable potassium-oxygen (K-O2 ) batteries promise to provide higher round-trip efficiency and cycle life than other alkali-oxygen batteries with satisfactory gravimetric energy density (935 Wh kg-1 ). Exploiting a strong electron-donating solvent, for example, dimethyl sulfoxide (DMSO) strongly stabilizes the discharge product (KO2 ), resulting in significant improvement in electrode kinetics and chemical/electrochemical reversibility. The first DMSO-based K-O2 battery demonstrates a much higher energy efficiency and stability than the glyme-based electrolyte. A universal KO2 growth model is developed and it is demonstrated that the ideal solvent for K-O2 batteries should strongly stabilize superoxide (strong donor ability) to obtain high electrode kinetics and reversibility while providing fast oxygen diffusion to achieve high discharge capacity. This work elucidates key electrolyte properties that control the efficiency and reversibility of K-O2 batteries.

Superoxide Stabilization and a Universal KO2 Growth Mechanism in Potassium–Oxygen Batteries

AbstractRechargeable potassium–oxygen (K‐O2) batteries promise to provide higher round‐trip efficiency and cycle life than other alkali–oxygen batteries with satisfactory gravimetric energy density (935 Wh kg−1). Exploiting a strong electron‐donating solvent, for example, dimethyl sulfoxide (DMSO) strongly stabilizes the discharge product (KO2), resulting in significant improvement in electrode kinetics and chemical/electrochemical reversibility. The first DMSO‐based K‐O2 battery demonstrates a much higher energy efficiency and stability than the glyme‐based electrolyte. A universal KO2 growth model is developed and it is demonstrated that the ideal solvent for K‐O2 batteries should strongly stabilize superoxide (strong donor ability) to obtain high electrode kinetics and reversibility while providing fast oxygen diffusion to achieve high discharge capacity. This work elucidates key electrolyte properties that control the efficiency and reversibility of K‐O2 batteries.

Stable Carbon Cathodes for Potassium-Oxygen Batteries

Among energy storage technologies beyond lithium-ion, alkali metal-oxygen batteries stand out for their unparalleled theoretical energy densities. Based on the reaction between dioxygen and alkali metal ions in non-aqueous electrolytes, metal-oxygen batteries could store up to 10 times more energy per unit mass (in the case of Li-O2) when compared to today’s lithium-ion batteries1. Despite extensive efforts elucidating the mechanism of the reaction between alkali cations and dioxygen, this technology is still far from maturing into a commercial device. The main drawbacks of Li-O2 systems are electrolyte and cathode instability, low conductivity of lithium peroxide (Li2O2) leading to poor cycleability. In contrast to Li-O2, potassium-O2 discharge reactions proceeds via a one electron reduction leading to potassium superoxide (KO2) as the sole discharge product2-5. Here, different carbon based cathodes were investigated in K-O2 cells. Furthermore the stability of the K metal anode with different non-aqueous electrolytes was compared. The cell capacity varied depending upon the cathodic carbon structure employed (Figure 1a). KO2 was the only discharge product identified via Raman spectroscopy (Figure 1b) and powder X-ray diffraction. FTIR spectra taken of the cathodes after first discharge, showed no evidence of carbonate species or other parasitic reaction products. These results are encouraging, since the large overpotential observed within Li-O2 cells was found to be related to side reactions on the carbon electrode surface6. The voltage gap in K-O2 cells was lower than 100 mV, and round trip efficiency, as high as 98%. The cycleability of the cells was found to be limited by side reactions between the potassium metal anode and ether-based electrolyte in the presence of dioxygen reduced species, rather than side reactions within the carbon cathode. The main components of this insulating anode surface layer were K2CO3, KOH and KO2. Similar anode surface layer composition was found for different combinations of ether electrolytes and potassium salts. However, while using super-concentrated electrolytes (3M and 5 M KTFSI in dimethoxyethane), O2 crossover was inhibited, and no KO2 was detected on the potassium metal anode surface. As a result, these cells were able to be cycled over 50 times under shallow cycling of 50 mAh/g. The superconcentrated electrolytes had no effect on the cathode reaction product, and the battery cycled through KO2 formation and oxidation. Capacity fade eventually occurred, as repetitive stripping/plating of K metal anode caused the disruption of the protective layer. This work highlights that once a suitable electrolyte has been selected, a metal-O2 cell can indeed be cycled numerous times. The challenge is to increase the cycleable capacity to more appealing values, whilst maintaining cell stability. [1] P.G. Bruce, S.A. Freunberger, L.J. Hardwick, J-M. Tarascon, Nature Mater. 11, 19 (2012). [2] X. Ren, Y. Wu, J. Am. Chem. Soc. 135, 2923 (2013). [3] X. Ren et al. ACS Appl. Mater. Interfaces 6, 19299 (2014). [4] W.D. McCulloch et al. ACS Appl. Mater. Interfaces 7, 26158 (2015). [5] X. Ren et. al. Adv. Energy. Mater. 1601080 (2016). [6] B.D. McCloskey et. al. J. Phys. Chem. Lett. 4, 2989 (2013). Figure 1

Improving Metal Anode Stability in Potassium Oxygen Batteries with Concentrated Electrolyte

In recent years, metal-oxygen batteries, especially non-aqueous lithium-oxygen batteries (or Li-O2 batteries), have drawn considerable research attention for future energy storage applications due to high theoretical specific energy densities. Compared to conventional lithium-oxygen batteries, potassium-oxygen (K-O2) batteries are based on a reversible O2/KO2 redox chemistry, resulting in much better round-trip efficiencies (higher than 90%) without using electrocatalysts. While the reversibility of the cathode reactions is improved, the cycling performance of K-O2 batteries is greatly limited by the K metal anode stability. The highly reducing K anode would react with electrolyte molecules and degrade seriously during cycling. Moreover, the oxygen crossover to the anode further accelerate the degradation process. Here, we report our studies about the improved K metal anode stability in K-O2 batteries with concentrated electrolytes. It is shown that in this class of electrolytes, a stable Solid Electrolyte Interface (SEI) layer is critical for protecting the K anode and suppressing the undesired side reactions. As a result, the metal anode cycling efficiency and the cycle life of K-O2 batteries can be largely increased.

Understanding Side Reactions in K–O2 Batteries for Improved Cycle Life

Superoxide based metal-air (or metal-oxygen) batteries, including potassium and sodium-oxygen batteries, have emerged as promising alternative chemistries in the metal-air battery family because of much improved round-trip efficiencies (>90%). In order to improve the cycle life of these batteries, it is crucial to understand and control the side reactions between the electrodes and the electrolyte. For potassium-oxygen batteries using ether-based electrolytes, the side reactions on the potassium anode have been identified as the main cause of battery failure. The composition of the side products formed on the anode, including some reaction intermediates, have been identified and quantified. Combined experimental studies and density functional theory (DFT) calculations show the side reactions are likely driven by the interaction of potassium with ether molecules and the crossover of oxygen from the cathode. To inhibit these side reactions, the incorporation of a polymeric potassium ion selective membrane (Nafion-K(+)) as a battery separator is demonstrated that significantly improves the battery cycle life. The K-O2 battery with the Nafion-K(+) separator can be discharged and charged for more than 40 cycles without increases in charging overpotential.