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Article

Reversible Conversion between Lithium Superoxide and Lithium Peroxide: A Closed “Lithium–Oxygen” Battery

by
Junkai Wang
1,
Rui Gao
1 and
Xiangfeng Liu
1,2,*
1
College of Materials Science and Opto-Electronic Technology, University of Chinese Academy of Sciences, Beijing 100049, China
2
CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing 100190, China
*
Author to whom correspondence should be addressed.
Inorganics 2023, 11(2), 69; https://doi.org/10.3390/inorganics11020069
Submission received: 5 December 2022 / Revised: 26 January 2023 / Accepted: 29 January 2023 / Published: 1 February 2023
(This article belongs to the Special Issue Advances in Metal Air Batteries)
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Versions Notes

Abstract

:
Lithium–air batteries have become a desirable research direction in the field of green energy due to their large specific capacity and high energy density. The current research mainly focuses on an open system continuously supplying high-purity oxygen or air. However, factors such as water and CO2 in the open system and liquid electrolytes’ evaporation will decrease battery performance. To improve the practical application of lithium–air batteries, developing a lithium–oxygen battery that does not need a gaseous oxygen supply is desirable. In this study, we designed a closed lithium–oxygen battery model based on the conversion of lithium superoxide and lithium peroxide (LiO2 + e− + Li+ ↔ Li2O2). Herein, the Pd-rGO as a catalyst will produce the LiO2 in the pre-discharge process, and the closed battery can cycle over 57 cycles stably. In addition to in situ Raman spectra, electrochemical quartz crystal microbalance (EQCM) and differential electrochemical mass spectrometry (DEMS) have been applied to explanation the conversion between LiO2 and Li2O2 during the charge–discharge process. This work paves the way to introduce a new closed “lithium–oxygen” battery system for developing large-capacity green energy.

Graphical Abstract

1. Introduction

Among the various battery types, the lithium–oxygen battery is considered a promising energy storage element due to its high theoretical capacity and energy density [1,2,3,4]. However, lithium–oxygen batteries have suffered from critical issues, such as sluggish oxygen reduction/evolution reaction (ORR/OER) kinetics, high overpotential, and limited cycle life. Currently, most research about lithium–oxygen batteries has found that a high-purity oxygen atmosphere is needed to reduce by-products, such as Li2CO3 and LiOH. In addition, the evaporation of the electrolyte is another challenge in the performance of Li-O2 batteries [5,6,7]. In terms of improving reaction activity and reducing overpotential, designing efficient catalysts is an effective strategy [8,9,10,11,12]. However, irreversible loss, such as the volatilization and decomposition of electrolytes, and the side reaction with other air components will occur during the reaction process in the open system [13,14,15,16,17]. From the point of practical applications, an O2 tank supplier not only occupies a large space but also decreases the specific energy density. Moreover, if the air is applied to replace the high-purity O2, these substances (Li2CO3 and LiOH) are not easily decomposed, resulting in irreversible capacity damage to the battery. Therefore, a new design of a closed lithium–oxygen battery without a continuous oxygen supplier is promising for practical application in the future.
The design idea of the closed battery is to quantitatively control the reactants and discharge products and eliminate the participation of gaseous oxygen. As for the electrochemical reaction mechanism of Li-O2, some studies have proposed that Li first reacts with O2 to form metastable LiO2 and subsequently transfers to Li2O2 through a second reduction or disproportionation, as shown in Equations (1)–(3) [6,18,19]. The LiO2 in the first step reaction is quite unstable. Even without the presence of O2, lithium superoxide (LiO2) can be further reacted to form peroxide (Li2O2) (Equation (2)). When the reaction rate is prolonged, a disproportionation reaction (Equation (3)) occurs in the discharge of superoxide (LiO2) which converts to oxygen and peroxide (Li2O2) [6,20,21,22,23,24]. Hence, maintaining the stable existence of superoxide as a reactant is the most crucial issue in a closed battery.
O2 + Li+ + e− = LiO2
LiO2 + Li+ + e− = Li2O2
2LiO2 = Li2O2 + O2
Recently, Kang et al. pointed out in a review [25] that the surrounding conditions, i.e., electrolytes, redox mediators, and catalysts, had a significant effect on the stability of intermediate LiO2 [10,26,27,28,29]. Lu et al. stabilized the formation of LiO2 using Ir-rGO as the cathode catalyst [27]. In general, Li-O2 batteries have been studied because the reaction path is affected by specific electrolytes, additives, and catalysts, which will change the reaction product, reduce the polarization potential, and improve the rate performance [30,31,32,33,34]. Our groups have successfully cycled an amorphous LiO2-based Li-O2 battery with a Pd-rGO hybrid catalyst [26]. This battery showed an ultra-low overpotential (~0.3 V), long cycle life, and high-rate capability. However, in this amorphous LiO2-based Li-O2 battery, O2 is still necessary to keep this electrochemical reaction. Just recently, Zhou’s group reported a high energy density and a long-life lithium-ion battery based on the conversion of Li2O to Li2O2 [35]. Due to concerns that oxygen leakage will affect battery performance, Zhou’s group gave up the 480 mAh g−1 capacity of Li2O to Li2O2. However, in our work, we improved the closed-type battery and proved that this part of the capacity has application value.
Taking advantage of the stabilization of amorphous LiO2 in our previous work, we propose to build a closed-type lithium–oxygen battery whose electrochemical reaction is mainly based on the conversion of LiO2 and Li2O2 (LiO2 + e− + Li+ ↔Li2O2). Compared with our previous work, this process extends the reversible cycle of a closed battery from LiO2 to the Li2O2 stage without gaseous oxygen [26]. The results indicate that the closed lithium–oxygen battery tested according to this strategy reached 57 cycles at a current density of 500 mA g−1. At the same time, we quantified the amount of oxygen released during the lithium superoxide phase by DEMS. In this work, the proposed new concept of a closed “Li-O2” battery system opens up a new avenue for the battery while promoting the application of catalysts and batteries based on the conversion of LiO2 and Li2O2.

2. Results and Discussion

The closed “Li-O2” batteries require stable lithium superoxide to participate in the reaction. To obtain the reactant lithium superoxide, we prepared Pd-rGO catalysts with Pd clusters by hydrothermal methods. As shown in Figure S1a, scanning electron microscope (SEM) images show that the synthesized Pd-rGO has a wrinkled 2D sheets structure of graphene. The diameter of the sheets is greater than 1 μm. In Figure S1b,c, the transmission electron microscope (TEM) shows about 5 nm of diameter palladium (Pd) particles. Corresponding to the XRD spectrum in Figure S1d, the characteristic peaks of the Pd at 40.118°, 46.658°, and 68.119° can be indexed to PDF#46-1043. The broad peak at about 21.8° corresponded to rGO.
The depth of discharge is an essential parameter for the reversible cycle of a closed battery. As shown in Figure 1 and Table 1, we use a unique catalyst (Pd-rGO) to pre-discharge (688 mAh g −1) to control the cathode deposition product at the lithium superoxide stage. (This step can also be taken as an activation process.) Then, the O2 supplier is shut off, and the battery is limited to 480 mAh g−1 for discharge and charge cycles. This electrochemical reaction is mainly based on the conversion of LiO2 and Li2O2 (LiO2 + e− + Li+ ↔ Li2O2). The battery is assembled, as we reported in a previous publication. The catalyst is loaded on carbon paper as a cathode and assembled into a battery for the pre-discharge test. After pre-discharge, the battery is sealed to maintain a closed environment. According to literature reports and theoretical capacity calculations (Table 1), it is determined that the theoretical capacity corresponding to LiO2 is 688 mAh g−1 [36]. The theoretical capacity for the conversion from LiO2 to Li2O2 is 480 mAh g−1. Therefore, the battery is limited to a specific capacity of 688 mAh g−1 for pre-discharge, and the specific capacity of the cycle is limited to 480 mAh g−1.
Then, the charge–discharge cycle performance of closed batteries was tested at different current densities. As shown in Figure 2a, the batteries discharged and charged with a current density of 100, 200, and 500 mA g−1, respectively. At 200 mA g−1, the charging potential of the battery was stable at 3.2 V. After the charging specific capacity reached 400 mAh g−1, the potential gradually increased to 4.1 V. At a current density of 500 mA g−1, the charging voltage gradually increases to 4.2 V. At a lower current density (100 mA g−1), the polarization potential (4.4 V) is higher than the high current density (200 or 500 mA g−1). This is because the charging time for low current density is longer, and the disproportionation reaction of the generated lithium superoxide to lithium peroxide is more pronounced. To demonstrate the importance of Pd cluster catalysts in closed batteries, the blank control group is rGO as a catalyst. In Figure 2b, the charging voltage of 100 mA g−1 has reached 4.4 V, and it can’t even be fully charged to 480 mAh g−1 at high current density. It demonstrates that the electrocatalytic activity of rGO is relatively weak. With the number of cycles increasing, the discharge platform is unchanged, but the charging potential increases. As shown in Figure 2c, the charging potential of the first cycle is 4.2 V, and the charging potential rises to 4.4 V after 50 cycles. Meanwhile, the discharge platform is reduced from 2.6 V to 2.4 V. It may be attributed to the continuous accumulation of side reactions, the electrolyte’s decomposition, and the catalyst’s deactivation. Figure 2d shows the long-cycle performance of closed batteries. At different current densities of 100, 200, and 500 mA g−1, the closed Li-O2 battery can be cycled to 20, 39, and 57 cycles, respectively.
To verify the reversibility of the closed battery, the production, decomposition, and change of the products during the charge and discharge processes of the lithium–oxygen battery can be detected by the in situ Raman spectrum. The battery is charged and discharged at a current density of 200 mA g−1, and the Raman spectrum is collected every 20 min. These characteristic peaks correspond to Li2O2 and O2− at 790–805 cm−1 and 1085–1105 cm−1, respectively [36,37,38,39]. After discharge, the signal peak of Li2O2 can be observed gradually, as shown in Figure 3a. The map of Figure 3b shows the signal changes more intuitively. As the depth of the discharge process occurs, the signals of Li2O2 increase. This indicates that the process of the discharge reaction corresponds to Equation (2). During the charging process, the Li2O2 signal (790–805 cm−1) gradually disappears and the O2− (1085–1105 cm−1) signal increases. It proves that the entire cycle is reversible. Moreover, Equation (3) is a side reaction usually accompanied by oxygen release, which should be avoided in practical applications.
In addition to Raman, UV–Vis spectroscopy is also a method to detect lithium peroxide. In Figure S2, UV–Vis spectroscopy can characterize the changes in Li2O2 in batteries. To confirm the conversion reaction of LiO2 to Li2O2 in a closed Li-O2 battery, we immersed cathodes with different specific capacity discharges in a mixed solution of TiOSO4/H2SO4 reagent and sulfuric acid. Then, the presence of lithium peroxide was measured by UV–Vis. In Figure S2, the Li2O2 cannot be observed at a pre-discharge. The signal of Li2O2 appears during closed discharge and disappears after closed charge. It verifies that LiO2 can be obtained by pre-discharge, and the product is converted reversibly between LiO2 and Li2O2 during the redox reaction process of the battery.
The EQCM is an intuitive way to characterize the production and decomposition of solid-phase products LiO2 and Li2O2. The results of the EQCM are shown in Figure 4. The orange squares are the data points of the mass change, and the green lines are the corresponding fitted curves. In the process of stable discharge, the mass has a linear relationship with the capacity. The EQCM theoretical slope table of different test environments and related products is shown in Table 2. After completing the pre-discharge in O2, we remove the O2 and simulate a closed oxygen-free environment with an Ar atmosphere. The discharge and charge cycle data are shown in Figure 4a,b. The slope values of the mass change during discharge and charge are 2.05 ng nAh−1 and 2.12 ng nAh−1, respectively. The theoretical slope for converting LiO2 to Li2O2 is 2.08 ng nAh−1. The slope value of the Pd-rGO in Ar is very close to the theoretical slope value of the conversion of lithium LiO2 to Li2O2. This corresponds to the single electron conversion process in the closed Pd-rGO battery. In addition, the Li-O2 battery with rGO in oxygen was used as a control group (Figure 4c,d). The slope of the product mass and capacity of the rGO battery (0.34 ng nAh−1) is lower than the theoretical slope of O2 to Li2O2 (0.855 ng nAh−1). The slope of the battery with rGO in O2 is close to the theoretical slope of O2 to LiOH. This shows that the discharge process of this battery is a multi-electron process.
To detect the gas changes and determine whether oxygen was released in the Pd-rGO closed battery, the electrochemical mass spectrometry (DEMS) was tested at 200 μA. First, the battery was pre-discharging under an O2/Ar mixed gas. As shown in Figure 5a,d, the pre-discharge O2 consumption is stable and linearly related to the capacity. After calculation, the number of electron transfers corresponding to oxygen consumption is 1.06 e−/O2. It indicates that the discharge product formed by the pre-discharge is LiO2. Then, the closed system is tested in a pure Ar environment. In theory, the reaction of the Pd-rGO closed battery is from LiO2 to Li2O2. This charging process is a reverse reaction with no oxygen released. However, in Figure 5c, we detected a small amount of O2 release during the charging phase. According to calculations, the reaction for the decomposition and release of oxygen by LiO2 accounts for about 16.32% (Figure 5f and Table 3). Correspondingly, in Figure 5b,e, the discharge process is accompanied by an approximate amount of oxygen consumption. After the oxygen supply is stopped, it is difficult to quickly remove the small amount of oxygen remaining in the battery. Therefore, part of the reaction of Equation (1) is mixed into the closing process.
The electrochemical performance of Pd-rGO in O2 and Pd-rGO closed batteries were examined in 2025-type Li-O2 batteries, as shown in Figure 6. From the cyclic voltammetry curves, it can conclude that the reaction is different between a closed system battery and an unclosed (pre-discharged) battery. As shown in Figure S3, the Pd-rGO-based Li-O2 battery exhibits a superior OER and ORR performance compared to the closed battery, with significant reduction peaks and oxidation peaks at 2.5 V and 3.4 V, respectively. This indicates that the reaction of the catalyst Pd-rGO in the pre-discharge process is based on O2/O2−. The decomposition process of the toroids Li2O2 produces a higher overpotential, while the film-like LiO2 has a lower overpotential [20,40]. Therefore, the Pd-rGO closed battery needs a higher charging potential to decompose Li2O2.

3. Materials and Methods

3.1. Synthesis of a Pd-rGO Hybrid Catalyst

A Pd-rGO hybrid catalyst is synthesized by a hydrothermal method [26]. In a typical process, 15 mL of GO suspension (5.6 mg/mL) and 5 ml of Pd solution (PdCl2 8.47 mg) were dispersed in 60 mL of deionized water, sonicated overnight, and stirred for 2 h. A total of 5 mL of hydrazine hydrate solution with a concentration of 85% was added dropwise to the suspension and stirred vigorously for 30 min. The mixed solution was poured into a stainless steel reaction kettle and heated at 180 °C for 12 h. After cooling to room temperature, it was separately centrifuged and washed twice with water and ethanol, and the solid product was freeze-dried for 24 h. The powder sample was placed in a tube furnace filled with an Ar atmosphere and heated at 400 °C for 1 h.
The control sample rGO was prepared in the same way without adding the Pd solution.

3.2. Structure Characterization of a Pd-rGO Catalyst

A Rigaku Smartlab powder diffractometer measured powder X-ray diffraction (XRD) with 2θ ranging from 10° to 80° and Cu Ka radiation (λ = 0.154 nm, 9 kW). The morphologies of Pd-rGO were observed on a scanning electron microscope (SEM SU8010 HITACHI) and transmission electron microscopy (TEM HT7700-Ex HITACHI). The acceleration voltage of SEM was 5 kV, 10 uA, with a work distance of 8 mm. The acceleration voltage of TEM was 100 kV.

3.3. Battery Fabrication and Electrochemical Measurements

The battery uses lithium metal as the negative electrode, and Pd-rGO (0.3 mg) loaded carbon paper (Torray) is the positive electrode. The separator is the glass filter separator (Whatsman). The cycle test of the closed battery uses a CR2025 coin cell. The electrolyte was a 1.0 M LITFSI/TEGDME solution with a water content of less than 50 ppm. The positive electrode was added dropwise with a slurry mixed from a dry sample, super p, and PVDF at a mass ratio of 4:4:2, and then dispersed in the NMP solution. A sample loaded with a mixture of super P and PVDF (8:2) was used as the control group. The porous cathode was dried under a vacuum at 120 °C for 12 h. The batteries were assembled in an argon-filled glove box with a water and oxygen content of less than 0.1 ppm. Electrochemical measurements were carried out on the LAND CT2001 battery tester system. The charge and discharge window are controlled at 2 V to 4.5 V. The battery was pre-discharged to 688 mAh g−1 in oxygen. Then, the cathode diffusion hole was sealed by aluminum foil, and the battery was cycled at 480 mAh g−1 in an oxygen-free environment. The cyclic voltammetry (CV) measurements were performed on a PRINCETON PMC-2000 electrochemical workstation.
The spectrophotometric method was used to detect the existence of Li2O2. The UV–Vis spectrum was carried out on Agilent Cary 60 UV–Vis with wavelengths ranging from 350 to 800 nm. A total of 10 g of Ti(IV)OSO4 was first dissolved in 500 mL of 1 M H2SO4 and filtered to obtain a settled solution. A total of 2.26 g of Li2O2 was then added to 10 mL of TiOSO4/H2SO4. 0.5, 1, 1.5, 2, and 2.5 mL of that solution were attenuated to 5 mL to obtain slandered samples. As for the spectrum of the cathode, the discharged/charged cathode was first encapsulated into a 10 mL glass penicillin bottle in the glove box. A total of 5 mL of TiOSO4/H2SO4 was injured into the bottle. After 15 min of shocking, the liquid in the bottle was used for UV testing. Raman spectra were obtained with a Renishaw inVia confocal Raman microscope with an excitation wavelength of 532 nm ranging from 600 to 2000 cm−1. DEMS was performed on an OmniStar GSD 320.
Electrochemical quartz crystal microbalance (EQCM) analyses were performed on a QCM922A-010 and PRINCETON PMC-2000. A Ti film quartz crystal (AT-cut 9 MHz) loaded with Pd-rGO or Super-P (<0.1 mg) was the working electrode. A platinum electrode coated with LiFePO4 was the counter electrode and reference electrode. The electrolyte was a 1.0 M LITFSI/TEGDME solution with a water content of less than 50 ppm. Before the experiment, the electrolyte was injected into Ar gas for 30 min. The environment of O2 and Ar is provided by pre-injecting 15 min of O2 or Ar into the electrolyte while maintaining the flow of oxygen and argon during charging and discharging.

4. Conclusions

In summary, we report a closed-type lithium–oxygen battery model based on the conversion between LiO2 and Li2O2. This conversion process has been analyzed by in situ Raman spectra, UV–Vis, electrochemical quartz crystal microbalance, and DEMS. At a current density of 500 mA g−1, the closed lithium–oxygen battery with Pd-rGO as a catalyst can be cycled more than 57 times. Hence, this work provides new insights and the possibility for further research and commercial applications of lithium–oxygen batteries without O2. Moreover, this strategy could also be applied to explore more highly efficient catalysts, electrolytes, and redox media in other batteries, such as Na-O2 and Zn–air batteries.

Supplementary Materials

The following supporting information can be downloaded at https://www.mdpi.com/article/10.3390/inorganics11020069/s1. Figure S1. (a) SEM images of Pd-rGO; (b) and (c) TEM image and HRTEM of Pd-rGO, respectively; (d) the XRD patterns of Pd-rGO; Figure S2. UV–Vis of Pd-rGO Li-O2 battery. Cathodes with different discharge-specific capacities are immersed in a mixed solution of TiOSO4/H2SO4 reagent and sulfuric acid; Figure S3. CV curves of Pd-rGO tested in an O2 environment and a closed battery in the LiTFSI/TEGDME electrolyte at a scan rate of 0.1 mV s−1; Figure S4. The cycle data of rGO closed batteries at 500 mA g−1.

Author Contributions

Conceptualization, R.G. and X.L.; methodology, J.W.; funding acquisition, X.L. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the Beijing Natural Science Foundation (grant No. 2182082), the National Natural Science Foundation of China (grants 11975238 and 11575192), the Scientific Instrument Developing Project (grant No. ZDKYYQ20170001), the International Partnership Program (grant No. 211211KYSB20170060), and the Strategic Priority Research Program (grant No. XDB28000000) of the Chinese Academy of Sciences. The Fundamental Research Funds also supported this work for the Central Universities.

Data Availability Statement

Not applicable.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Bruce, P.G.; Freunberger, S.A.; Hardwick, L.J.; Jean-Marie, T. Li-O2 and Li-S batteries with high energy storage. Nat. Mater. 2011, 11, 19–29. [Google Scholar] [CrossRef] [PubMed]
  2. Geng, D.; Ding, N.; Hor, T.A.; Chien, S.W.; Liu, Z.; Wuu, D.; Sun, X.; Zong, Y. From Lithium-Oxygen to Lithium-Air Batteries: Challenges and Opportunities. Adv. Energy Mater. 2016, 6, 1502164. [Google Scholar] [CrossRef]
  3. Grande, L.; Paillard, E.; Hassoun, J.; Park, J.-B.; Lee, Y.-J.; Sun, Y.-K.; Passerini, S.; Scrosati, B. The lithium/air battery: Still an emerging system or a practical reality? Adv. Mater. 2015, 27, 784–800. [Google Scholar] [CrossRef] [PubMed]
  4. Huang, Y.; Wang, Y.; Tang, C.; Wang, J.; Zhang, Q.; Wang, Y.; Zhang, J. Atomic Modulation and Structure Design of Carbons for Bifunctional Electrocatalysis in Metal–Air Batteries. Adv. Mater. 2019, 31, 1803800. [Google Scholar] [CrossRef]
  5. Léon, A.; Fiedler, A.; Blum, M.; Benkert, A.; Meyer, F.; Yang, W.; Bär, M.; Scheiba, F.; Ehrenberg, H.; Weinhardt, L.; et al. Valence Electronic Structure of Li2O2, Li2O, Li2CO3, and LiOH Probed by Soft X-ray Emission Spectroscopy. J. Phys. Chem. C 2017, 121, 5460–5466. [Google Scholar] [CrossRef]
  6. Cui, Q.; Zhang, Y.; Ma, S.; Peng, Z. Li2 O2 oxidation: The charging reaction in the aprotic Li-O2 batteries. Sci. Bull. 2015, 60, 1227–1234. [Google Scholar] [CrossRef]
  7. Zhang, X.; Gong, Y.; Li, S.; Sun, C. Porous Perovskite La0.6Sr0.4Co0.8Mn0.2O3 Nanofibers Loaded with RuO2 Nanosheets as an Efficient and Durable Bifunctional Catalyst for Rechargeable Li–O2 Batteries. ACS Catal. 2017, 7, 7737–7747. [Google Scholar] [CrossRef]
  8. Ma, R.; Sasaki, T. Nanosheets of oxides and hydroxides: Ultimate 2D charge-bearing functional crystallites. Adv. Mater. 2010, 22, 5082–5104. [Google Scholar] [CrossRef]
  9. Liu, Y.; Xiao, C.; Li, Z.; Xie, Y. Vacancy engineering for tuning electron and phonon structures of two-dimensional materials. Adv. Energy Mater. 2016, 6, 1600436. [Google Scholar] [CrossRef]
  10. Lim, H.-D.; Lee, B.; Zheng, Y.; Hong, J.; Kim, J.; Gwon, H.; Ko, Y.; Lee, M.; Cho, K.; Kang, K. Rational design of redox mediators for advanced Li–O2 batteries. Nat. Energy 2016, 1, 16066. Available online: https://www.nature.com/articles/nenergy201666#supplementary-information (accessed on 23 December 2015). [CrossRef]
  11. Cheng, F.; Zhang, T.; Zhang, Y.; Du, J.; Han, X.; Chen, J. Enhancing electrocatalytic oxygen reduction on MnO(2) with vacancies. Angew. Chem. Int. Ed. Engl. 2013, 52, 2474–2477. [Google Scholar] [CrossRef] [PubMed]
  12. Sun, C.; Li, F.; Ma, C.; Wang, Y.; Ren, Y.; Yang, W.; Ma, Z.; Li, J.; Chen, Y.; Kim, Y.; et al. Graphene–Co3O4 nanocomposite as an efficient bifunctional catalyst for lithium–air batteries. J. Mater. Chem. A 2014, 2, 7188–7196. [Google Scholar] [CrossRef]
  13. Cheng, F.; Chen, J. Metal-air batteries: From oxygen reduction electrochemistry to cathode catalysts. Chem. Soc. Rev. 2012, 41, 2172–2192. [Google Scholar] [CrossRef] [PubMed]
  14. Thotiyl, M.M.O.; Freunberger, S.A.; Peng, Z.; Bruce, P.G. The carbon electrode in nonaqueous Li-O2 cells. J. Am. Chem. Soc. 2013, 135, 494–500. [Google Scholar] [CrossRef]
  15. McCloskey, B.D.; Speidel, A.; Scheffler, R.; Miller, D.C.; Viswanathan, V.; Hummelshøj, J.S.; Nørskov, J.K.; Luntz, A.C. Twin Problems of Interfacial Carbonate Formation in Nonaqueous Li-O2 Batteries. J. Phys. Chem. Lett. 2012, 3, 997–1001. [Google Scholar] [CrossRef]
  16. Peng, Z.; Freunberger, S.A.; Chen, Y.; Bruce, P.G. A reversible and higher-rate Li-O2 battery. Science 2012, 337, 563–566. [Google Scholar] [CrossRef]
  17. Asadi, M.; Sayahpour, B.; Abbasi, P.; Ngo, A.T.; Karis, K.; Jokisaari, J.R.; Liu, C.; Narayanan, B.; Gerard, M.; Yasaei, P.; et al. A lithium–oxygen battery with a long cycle life in an air-like atmosphere. Nature 2018, 555, 502–506. [Google Scholar] [CrossRef]
  18. Lu, Y.-C.; Gasteiger, H.A.; Crumlin, E.; McGuire, R., Jr.; Shao-Horn, Y. Electrocatalytic Activity Studies of Select Metal Surfaces and Implications in Li-Air Batteries. J. Electrochem. Soc. 2010, 157, A1016–A1025. [Google Scholar] [CrossRef]
  19. 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. J. Am. Chem. Soc. 2012, 134, 2902–2905. [Google Scholar] [CrossRef]
  20. Zhang, Y.; Zhang, X.; Wang, J.; McKee, W.C.; Xu, Y.; Peng, Z. Potential-Dependent Generation of O2– and LiO2 and Their Critical Roles in O2 Reduction to Li2O2 in Aprotic Li–O2 Batteries. J. Phys. Chem. C 2016, 120, 3690–3698. [Google Scholar] [CrossRef]
  21. Peng, Z.; Chen, Y.; Bruce, P.G.; Xu, Y. Direct Detection of the Superoxide Anion as a Stable Intermediate in the Electroreduction of Oxygen in a Non-Aqueous Electrolyte Containing Phenol as a Proton Source. Angew. Chem. Int. Ed. Engl. 2015, 54, 8165–8168. [Google Scholar] [CrossRef] [PubMed]
  22. Oh, S.H.; Black, R.; Pomerantseva, E.; Lee, J.-H.; Nazar, L. Synthesis of a metallic mesoporous pyrochlore as a catalyst for lithium-O2 batteries. Nat. Chem. 2012, 4, 1004–1010. [Google Scholar] [CrossRef] [PubMed]
  23. Yao, W.; Yuan, Y.; Tan, G.; Liu, C.; Cheng, M.; Yurkiv, V.; Bi, X.; Long, F.; Friedrich, C.R.; Mashayek, F.; et al. Tuning Li2O2 Formation Routes by Facet Engineering of MnO2 Cathode Catalysts. J. Am. Chem. Soc. 2019, 141, 12832–12838. [Google Scholar] [CrossRef] [PubMed]
  24. Gong, Y.; Ding, W.; Li, Z.; Su, R.; Zhang, X.; Wang, J.; Zhou, J.; Wang, Z.; Gao, Y.; Li, S.; et al. Inverse Spinel Cobalt–Iron Oxide and N-Doped Graphene Composite as an Efficient and Durable Bifuctional Catalyst for Li–O2 Batteries. ACS Catal. 2018, 8, 4082–4090. [Google Scholar] [CrossRef]
  25. Lim, H.-D.; Lee, B.; Bae, Y.; Park, H.; Ko, Y.; Kim, H.; Kim, J.; Kang, K. Reaction chemistry in rechargeable Li-O2 batteries. Chem. Soc. Rev. 2017, 46, 2873–2888. [Google Scholar] [CrossRef]
  26. Gao, R.; Liang, X.; Yin, P.; Wang, J.; Lee, Y.L.; Hu, Z.; Liu, X. An amorphous LiO2-based Li-O2 battery with low overpotential and high rate capability. Nano Energy 2017, 41, 535–542. [Google Scholar] [CrossRef]
  27. Lu, J.; Lee, Y.J.; Luo, X.; Lau, K.C.; Asadi, M.; Wang, H.-H.; Brombosz, S.; Wen, J.; Zhai, D.; Chen, Z.; et al. A lithium-oxygen battery based on lithium superoxide. Nature 2016, 529, 377–382. [Google Scholar] [CrossRef]
  28. Gao, X.; Chen, Y.; Johnson, L.R.; Jovanov, Z.P.; Bruce, P.G. A rechargeable lithium–oxygen battery with dual mediators stabilizing the carbon cathode. Nat. Energy 2017, 2, 17118. [Google Scholar] [CrossRef]
  29. Li, F.; Tang, D.-M.; Chen, Y.; Golberg, D.; Kitaura, H.; Zhang, T.; Yamada, A.; Zhou, H. Ru/ITO: A carbon-free cathode for nonaqueous Li-O2 battery. Nano Lett. 2013, 13, 4702–4707. [Google Scholar] [CrossRef]
  30. Liu, T.; Leskes, M.; Yu, W.; Moore, A.J.; Zhou, L.; Bayley, P.M.; Kim, G.; Grey, C.P. Cycling Li-O2 batteries via LiOH formation and decomposition. Science 2015, 350, 530–533. [Google Scholar] [CrossRef] [Green Version]
  31. Khetan, A.; Luntz, A.; Viswanathan, V. Trade-Offs in Capacity and Rechargeability in Nonaqueous Li-O2 Batteries: Solution-Driven Growth versus Nucleophilic Stability. J. Phys. Chem. Lett. 2015, 6, 1254–1259. [Google Scholar] [CrossRef] [PubMed]
  32. Wu, S.; Tang, J.; Li, F.; Liu, X.; Yamauchi, Y.; Ishida, M.; Zhou, H. A Synergistic System for Lithium-Oxygen Batteries in Humid Atmosphere Integrating a Composite Cathode and a Hydrophobic Ionic Liquid-Based Electrolyte. Adv. Funct. Mater. 2016, 26, 3291–3298. [Google Scholar] [CrossRef]
  33. Lutz, L.; Yin, W.; Grimaud, A.; Alves Dalla Corte, D.; Tang, M.; Johnson, L.; Azaceta, E.; Sarou-Kanian, V.; Naylor, A.J.; Hamad, S.; et al. Capacity Na–O2 Batteries: Key Parameters for Solution-Mediated Discharge. J. Phys. Chem. C 2016, 120, 20068–20076. [Google Scholar] [CrossRef]
  34. Gittleson, F.S.; Jones, R.E.; Ward, D.K.; Foster, M.E. Oxygen solubility and transport in Li–air battery electrolytes: Establishing criteria and strategies for electrolyte design. Energ. Environ. Sci. 2017, 10, 1167–1179. [Google Scholar] [CrossRef]
  35. Qiao, Y.; Jiang, K.; Deng, H.; Zhou, H. A high-energy-density and long-life lithium-ion battery via reversible oxide–peroxide conversion. Nat. Catal. 2019, 2, 1035–1044. [Google Scholar] [CrossRef]
  36. Han, X.-B.; Kannari, K.; Ye, S. In situ surface-enhanced Raman spectroscopy in Li–O2 battery research. Curr. Opin. Electrochem. 2019, 17, 174–183. [Google Scholar] [CrossRef]
  37. Lau, K.C.; Qiu, D.; Luo, X.; Greeley, J.; Curtiss, L.A.; Lu, J.; Amine, K. Theoretical Exploration of Various Lithium Peroxide Crystal Structures in a Li-Air Battery. Energies 2015, 8, 529–548. [Google Scholar] [CrossRef]
  38. Johnson, L.; Li, C.; Liu, Z.; Chen, Y.; Freunberger, S.; Ashok, P.C.; Praveen, B.B.; Dholakia, K.; Tarascon, J.-M.; Bruce, P.G. The role of LiO2 solubility in O2 reduction in aprotic solvents and its consequences for Li-O2 batteries. Nat. Chem. 2014, 6, 1091–1099. [Google Scholar] [CrossRef]
  39. Qiao, Y.; He, Y.; Wu, S.; Jiang, K.; Li, X.; Guo, S.; He, P.; Zhou, H. MOF-Based Separator in an Li–O2 Battery: An Effective Strategy to Restrain the Shuttling of Dual Redox Mediators. ACS Energy Lett. 2018, 3, 463–468. [Google Scholar] [CrossRef]
  40. Peng, Z.; Freunberger, S.; Hardwick, L.; Chen, Y.; Giordani, V.; Bardé, F.; Novák, P.; Graham, D.; Tarascon, J.-M.; Bruce, P.G. Oxygen reactions in a non-aqueous Li+ electrolyte. Angew. Chem. Int. Ed. Engl. 2011, 50, 6351–6355. [Google Scholar] [CrossRef]
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Figure 1. Schematic representations of a closed “Li–O2” battery based on the conversion of LiO2 and Li2O2 (LiO2 + e− + Li+ ↔ Li2O2).
Figure 1. Schematic representations of a closed “Li–O2” battery based on the conversion of LiO2 and Li2O2 (LiO2 + e− + Li+ ↔ Li2O2).
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Figure 2. The specific capacity is cut off at 480 mAh g−1. The first cycle charge and discharge curves at 100, 200, 500 mA g−1; (a) Pd–rGO for Li–O2 battery; (b) rGO for Li–O2 battery; (c) the dis–charge/charge curves at different cycles of Pd–rGO for Li–O2 battery at 500 mA g−1; (d) the cycle performances of Pd–rGO and rGO for Li–O2 battery at different current density.
Figure 2. The specific capacity is cut off at 480 mAh g−1. The first cycle charge and discharge curves at 100, 200, 500 mA g−1; (a) Pd–rGO for Li–O2 battery; (b) rGO for Li–O2 battery; (c) the dis–charge/charge curves at different cycles of Pd–rGO for Li–O2 battery at 500 mA g−1; (d) the cycle performances of Pd–rGO and rGO for Li–O2 battery at different current density.
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Figure 3. The in situ Raman spectrum of Pd–rGO catalyzed for Li–O2 battery. (a) The in situ Raman overlay graph. (b) The in situ Raman mapping and corresponding voltage curves.
Figure 3. The in situ Raman spectrum of Pd–rGO catalyzed for Li–O2 battery. (a) The in situ Raman overlay graph. (b) The in situ Raman mapping and corresponding voltage curves.
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Figure 4. Mass change of Ti film quartz crystal in the LiTFSI/TEGDME electrolyte at a 1 μA. (a,b) Discharge and charge curves and mass changes of Li-O2 battery with Pd–rGO as a catalyst in Ar (simulate closed battery status). (c,d) Discharge and charge curves and mass changes of Li –O2 battery with rGO as a catalyst in O2 (simulate open Li-O2 battery status).
Figure 4. Mass change of Ti film quartz crystal in the LiTFSI/TEGDME electrolyte at a 1 μA. (a,b) Discharge and charge curves and mass changes of Li-O2 battery with Pd–rGO as a catalyst in Ar (simulate closed battery status). (c,d) Discharge and charge curves and mass changes of Li –O2 battery with rGO as a catalyst in O2 (simulate open Li-O2 battery status).
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Figure 5. DEMS analyses in Pd–rGO closed battery. The amount of O2 consumed and released in different processes: (a) pre–discharge; (b) closed–discharge; (c) closed–charge; (d–f) is the corre–sponding gas and capacitance curve.
Figure 5. DEMS analyses in Pd–rGO closed battery. The amount of O2 consumed and released in different processes: (a) pre–discharge; (b) closed–discharge; (c) closed–charge; (d–f) is the corre–sponding gas and capacitance curve.
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Figure 6. Batteries have two different stages of discharge products: LiO2 and Li2O2. The conversion from LiO2 to Li2O2 does not require O2. This can realize the reversible cycle of a closed battery with a capacity of 480 mAh g−1.
Figure 6. Batteries have two different stages of discharge products: LiO2 and Li2O2. The conversion from LiO2 to Li2O2 does not require O2. This can realize the reversible cycle of a closed battery with a capacity of 480 mAh g−1.
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Table
Table 1. The theoretical discharge capacity of three reaction paths.
Table 1. The theoretical discharge capacity of three reaction paths.
ProcessTheoretical Specific Capacity
(mAh g−1)
O2 +Li+ + e−→LiO2Pre-Discharge688.4021
O2 + 2Li+ + e−→Li2O2Open-Discharge (With O2)1168.5377
LiO2→Li2O2Closed-Cycle (No O2)480.1356
Table
Table 2. The EQCM experimental matrix of different products.
Table 2. The EQCM experimental matrix of different products.
M (mol∙g−1)N (mol)C (mAh g−1)1/C (ng nAh−1)
LiO238.93881688.40211.4526
Li2O245.878821168.53770.8558
2LiOH47.894642238.70830.4467
LiO2→Li2O26.94001480.13562.0827
Pd-rGO in Ar 2.0522
rGO in O2 0.3427
Faraday’s laws of electrolysis: C = nF/3.6 M; C: theoretical capacity; n: the number of electrons transferred; F: Faraday’s constant (F = 96485 C mol−1); M: molar mass; n: the number of electrons transferred; 1/C: the reciprocal of theoretical capacity is the slope in the EQCM.
Table
Table 3. DEMS data of a Pd-rGO closed battery.
Table 3. DEMS data of a Pd-rGO closed battery.
SampleΔQ (e−)ΔO2 (nmol)n (e− mol−1)
Closed Pre 7.46 × 10−67053.46 (O2→LiO2)1.06
Closed Discharge0.76 × 10−6762.06 (O2→LiO2)1.00
Closed Charge0.71 × 10−6711.06 (LiO2→O2)1.00
Number of electron transfers: n = ΔQ/ΔO2; Q: total number of electrons.
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Wang, J.; Gao, R.; Liu, X. Reversible Conversion between Lithium Superoxide and Lithium Peroxide: A Closed “Lithium–Oxygen” Battery. Inorganics 2023, 11, 69. https://doi.org/10.3390/inorganics11020069

AMA Style

Wang J, Gao R, Liu X. Reversible Conversion between Lithium Superoxide and Lithium Peroxide: A Closed “Lithium–Oxygen” Battery. Inorganics. 2023; 11(2):69. https://doi.org/10.3390/inorganics11020069

Chicago/Turabian Style

Wang, Junkai, Rui Gao, and Xiangfeng Liu. 2023. "Reversible Conversion between Lithium Superoxide and Lithium Peroxide: A Closed “Lithium–Oxygen” Battery" Inorganics 11, no. 2: 69. https://doi.org/10.3390/inorganics11020069

APA Style

Wang, J., Gao, R., & Liu, X. (2023). Reversible Conversion between Lithium Superoxide and Lithium Peroxide: A Closed “Lithium–Oxygen” Battery. Inorganics, 11(2), 69. https://doi.org/10.3390/inorganics11020069

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