Unveiling the Complex Effects of H2O on DischargeâRecharge

Subscriber access provided by READING UNIV

Energy Conversion and Storage; Plasmonics and Optoelectronics 2

Unveiling the Complex Effects of HO on DischargeRecharge Behaviors of Aprotic Lithium-O Batteries 2

Shunchao Ma, Jiawei Wang, Jun Huang, Zhen Zhou, and Zhangquan Peng J. Phys. Chem. Lett., Just Accepted Manuscript • DOI: 10.1021/acs.jpclett.8b01333 • Publication Date (Web): 24 May 2018 Downloaded from http://pubs.acs.org on May 24, 2018

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

The Journal of Physical Chemistry Letters

Unveiling the Complex Effects of H2O on Discharge-Recharge Behaviors of Aprotic Lithium-O2 Batteries Shunchao Ma,†,‖, ⊥ Jiawei Wang,†, ⊥ Jun Huang,‡ Zhen Zhou,§ and Zhangquan Peng*,† †

State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin 130022, P. R. China ‖

‡

University of Chinese Academy of Sciences, Beijing 100039, P. R. China

College of Chemistry and Chemical Engineering, Central South University, Changsha 410083, China

§

Institute of New Energy Material Chemistry, School of Materials Science and Engineering, Key Laboratory of Advanced Energy Materials Chemistry (Ministry of Education), Nankai University, Tianjin 300071, China

*Corresponding author E-mail address: [email protected]

ACS Paragon Plus Environment

1

The Journal of Physical Chemistry Letters 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 2 of 24

ABSTRACT The addition of H2O, even trace amount, in aprotic Li-O2 batteries has a remarkable impact on achieving high capacity by triggering solution mechanism, and even reducing charge overpotential. However, the critical role of H2O in promoting solution mechanism still lacks persuasive spectroscopic evidence, moreover, the origin of low polarization remains incompletely understood. Herein, by in situ spectroscopic identification of reaction intermediates, we directly verify that H2O additive is able to alter oxygen reduction reaction (ORR) pathway subjected to solution-mediated growth mechanism of Li2O2. In addition, ingress of H2O also induces to form partial LiOH, resulting in reduced charging polarization due to its higher conductivity, however, LiOH could not contribute to O2 evolution upon recharge. These original results unveil the complex effects of H2O on cycling the aprotic Li-O2 batteries, which are instructive for the mechanism study of Li-O2 batteries with protic additives or soluble catalysts.

TOC GRAPHICS

KEYWORDS Li-O2

batteries,

H2O

additive,

oxygen

electrochemistry,

low

polarization,

in

situ

characterizations


2

Page 3 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


The rechargeable aprotic Li-O2 battery has captured worldwide attention due to its ultrahigh theoretical specific capacity and specific energy.1-6 A recent careful calculation has shown that the specific capacity of a Li-O2 battery can reach up to 700 mAh/g (with respect to the total mass of the oxygen cathode), which is 2-3 times larger than what a Li-ion battery can deliver.7-9 However, realizing this game-changing technique is rather challenging, because it combines several most difficult issues in energy storage and conversion, namely, the lithium metal anode that remains difficult to rein for several decades, the sluggish oxygen reduction and evolution involving Li2O2, a wide-bandgap insulator,10,11 and the severe electrolyte degradation induced by very active reaction intermediates.12,13 Notwithstanding, steady progress has been made concerning the aformentioned issues in recent years, endorsing the hope that the Li-O2 battery will not just be a laboratory toy.7,9,14-17 Understanding the mechanism and implication of Li2O2 formation has been one of the most vigorous themes in the realm of Li-O2 batteries in the past years.9,17-23 Both a surface- and a solution-mediated mechanism have been discerned for the discharge process, with the former forming Li2O2 films on the electrode surface and the latter Li2O2 toroids precipitating in the solution phase.20,21 Nevertheless, Li2O2 films severely impede charge transport and thus cause premature death upon discharge.24,25 Consequently, several strategies have been conceived to circumvent the surface-mediated pathway, such as, by employing strongly-solvating solvents or anionic salts,21,26.27 by introducing redox shuttles,28-31 and by adding H2O or phenol as protic additives. 32,33 In particular, unveiling the role of H2O in modulating the reaction pathway and then determining the battery performance is of both fundamental and practial importance, because H2O-related issues are inevitable for any Li-O2 battery operated in ambient atmosphere. Aetukuri


3


Page 4 of 24

et al. reported that the presence of H2O in aprotic electrolyte leads to the formation of toroid-like Li2O2 and apparent increase in the discharge capacity.32 Similar phenomena were also observed by Schwenke et al.34 From the kinetics viewpoint, Kwabi et al. speculated that H2O brings down the nucleation rate of Li2O2 on the electrode surface, and then drives the reaction mechanism to the solution-mediated pathway.35 From the themodynamics viewpoint, Qiao et al. proposed that the presence of H2O changes the reaction pathway to a single two-electron transfer process with hydroperoxide (HO2-), instead of O2- as the intermediate, effectively reducing parasitic reactions and improving the dischage capacity simultaneously.36 However, the picture of H2O effect in Li-O2 batteries is still far from complete. Firstly, the solution-mediated mechanism was invoked to explain the formation of Li2O2 toroids in the presence of H2O in previous reports,32,34,35 while in situ spectroscopic evidences of reaction intermediates and pathways are lacking yet. Secondly, the final discharge products are not in agreement in different reports. Aetukuri et al.32 showed that the discharge product is exclusively composed of Li2O2 regardless of the H2O content. On the contrary, Liu et al. and Li et al. pointed out that large LiOH crystals dominate the discharge product in the case of introducing H2O and specific catalysts.37,38 Thirdly, little is known about the H2O effect on the recharge. Qiao et al. demonstrated that adding H2O decreases the charge overpotential as well, which seems to contradict with the conventional wisdom that oxidiation of toroidal Li2O2 particles brings about an extraordinarily high overpotential up to 1.0 V.36 Hence, the primary aim of this work is to further scrutinize the effects of H2O on cycling the aprotic Li-O2 batteries. In situ surface enhanced Raman spectroscopy (SERS) to monitor the reaction interface reveals that the signature of surface-Li2O2 disappears completely during O2 reduction reaction (ORR) with 10 M H2O in the electrolyte. This spectroscopic investigation


4

Page 5 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


provides convictive evidence that H2O can promote Li2O2 formation via the solution-mediated mechanism on discharging. In addition, a combined analysis using in situ differential electrochemical mass spectrometry (DEMS) and direct conductivity measurement unveils that LiOH, which coexists with Li2O2 in the discharge product for the case of H2O addition, is responsible for the lowered charge overpotential because of its intrinsic higher conductivity comparing with solid Li2O2. To get mechanistic insights into the impact of H2O on ORR in aprotic Li-O2 batteries, cyclic voltammetry (CV) and corresponding in situ SERS at various potentials were performed with the aim to identify respective ORR species. Firstly, for a strictly dry, O2-saturated 0.1 M LiClO4 dimethyl sulfoxide (DMSO) electrolyte, as shown in Figures 1a and 1b, the CV plots exhibit two reduction peaks(see the inserted curve in Figure 1a for more clearly) during cathodic scanning and three oxidation peaks during reverse anodic scanning, which are consistent with previous results in DMSO.20 Correspondingly, the obtained in situ SERS demonstrates that only absorbed superoxide (O2-*) species is observed at the onset potential (red curve in Figure 1b), implying that Li2O2 forms at this low overpotential region steered by a sluggish solution-mediated disproportionation mechanism via stable O2-* intermediate.20,21 However, at high overpotentials, Li2O2 species accompanying with O2-* also appears on the SERS curve (blue curve in Figure 1b), which directly forms on Au electrode dominated by a fast surface-mediated mechanism.20,21 Then, the reduction current reduces drastically to the terminated cathodic potential owing to the coverage of insulative Li2O2 films on the electrode, at this point, only Li2O2 signature is observed on the SERS curve (olive curve in Figure 1b).


5


Page 6 of 24

Figure 1. CV curves on an Au electrode in an O2-saturated 0.1 M LiClO4 DMSO electrolytes containing various amounts of H2O at scan rate of 50 mV/s and corresponding SERS collected at different cathodic cut-off potentials, (a),(b) 0 M H2O; (c),(d) 1 M H2O; (e),(f) 10 M H2O.

Once H2O was introduced into the O2-saturated 0.1 M LiClO4 DMSO electrolyte, the collected CVs and SERS with different H2O contents revealed significantly divergent. With a moderate content of 1 M H2O, the obtained CV curve (Figure 1c) is different from that of dry electrolyte condition. For the ORR part of potential scan, two reduction peaks were wellresolved with the second reduction peak negatively shifted to 2.27 V, in contrast to the one located at 2.35 V of strictly dry DMSO in Figure 1a. Moreover, another distinctive feature


6

Page 7 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


associated with the CV of ORR is the cathodic current reduced smoothly within the potential region below the second reduction peak. For more scrutiny on the ORR mechanism under H2O presence, the SERS was collected, as shown in Figure 1d. Intriguingly, the O2-* species can be persistently detected on the surface of Au electrode, even at one higher overpotential (olive curve in Figure 1d). It is generally acceptable that the absorbed O2-* tends to rapidly transform to surface-Li2O2 via a surface-mediated mechanism, vanishing its Raman signiture, at high overpotentials in anhydrous electrolyte as discussed above (Figure 1a and 1b) and also in previous reports.20,21 Therefore, this presistent O2-* rationalizes that H2O intrusion suppresses the Li2O2 surface-mediated mechanism, but promotes the solution-mediated mechanism even at high overpotential. As for O2 evolution reaction (OER), a new oxidation peak located at 2.80 V emerged, which corresponds to the oxidation of O2-, and this corollary has been confirmed based on SERS in TBAClO4 DMSO electrolyte (Figure S1). In typical O2-saturated TBAClO4 DMSO electrolyte, the redox of O2/O2- couple exhibited excellent reversibility, and the oxidation peak located at approximate 2.8V was decerned as the oxidation of O2- via CV coupled with SERS, as shown in Figure S1. The other two distorted oxidation peaks located between 3.0 V to 4.0 V in Figure 1c are associated with the oxidation of Li2O2.20 By comparing the diverse CV behaviors and SERS results whether H2O existed or not, we confirmed that O2- was stabilized within broad potential region in LiClO4 DMSO electrolytes with H2O addition, and therefore promoted Li2O2 formation subjected to the solution-mediated mechanism even at high overpotentials. Furthermore, when the H2O content was increased to 10 M, to our surprise, the CV curve presents a sole reduction peak during the entire ORR (Figure 1e), and that corresponding to the reduction of O2 to O2-, based on the in situ SERS results (Figure 1f). Noticeably, a plethora of H2O (10 M) could facilitate the stabilization of soluble O2- resulting in Li2O2 solution-driven


7


Page 8 of 24

pathway, in additon, excess H2O might also improve the solubility of Li2O2 by protonation,33,34 thus annihilating the characteristic signal of absorbed Li2O2 on electrode. Unfortunately, no extra Raman signal of new abosorbed species, for instance, LiOH or HO2- can be detected according to present SERS results, because the produced soluble species might diffuse into the bulk electrolyte which were beyond the detection range of SERS. However, inductively coupled plasma (ICP) ancillary tests provided clear evidence for the promoted dissolution of solid Li2O2 in H2O-involved DMSO solvents (Figure S2). While in the anodic scan, two oxidation peaks are observed (see in Figure 1e). Based on the aforementioned discussions, it is certain that the first oxidation peak located at 2.82 V is related to the oxidation of O2-. The second oxidation peak located at 3.22 V probably attributes to the oxidation of soluble Li2O2 in electrolytes. To verify this assumption, a linear potential scan of Au electrode in Li2O2 super-saturated 10 M H2OTBAClO4 DMSO solution was conducted. As shown in Figure S3 (the red curve), two oxidation peaks located at 3.22 V and 3.73 V are observed, ascribed to the oxidation of soluble Li2O2 in electrolytes and bulk Li2O2, respectively, due to the limited solubility of Li2O2 in DMSO electrolyte. The above CVs coupled with in situ SERS studies for the first time provide direct in situ spectroscopic evidence that H2O additive in Li-O2 batteries is able to alter the ORR pathway subjected to solution-mediated growth mechanism of Li2O2, by operando identifying intermediates and products absorbed on the electrode surface. Due to the ingress of H2O, the Raman signal of deposited Li2O2 ascribed to the surface-driven mechanism vanishes at high overpotentials, whereas only soluble O2- intermediate for solution mechanism persistently exists upon the entire discharge. These salient features unveil that H2O significantly enhances the solution-mediated mechanism of ORR, under an extreme condition of high H2O content (10 M),


8

Page 9 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Li2O2 forms dominantly through the solution-mediated mechanism, prevailing over the surface mechanism during the gamut of discharge.

Figure 2. SEM images of the discharge products for Li-O2 cells with various H2O contents, (a) 0 M H2O, (b) 1 M H2O and (c) 10 M H2O. (d) XRD patterns and (e) FTIR spectra of extracted cathodes after discharging at 100mA/g.

Moreover, H2O induced solution-driven Li2O2 growth was visually confirmed by scanning eletron microscope (SEM, Figures 2a-c) after discharging the swagelok-type Li-O2 cells. Without H2O, nanoscale Li2O2 flakes are observed (Figure 2a), whereas, micron-sized toroid-like particles of dsicharged products are deposited on the carbon electrode when introducing H2O additive, shown in Figures 2b and 2c. The above SEM results validate that the solution-driven mechanism is induced by H2O, which is consistent with previous reports.32,35,36 To our knowledge, the category of ultimate discharge products is another controversial issue, since Li2O2, 32,35,36 LiOH,37,38 or the mixture of LiOH and Li2O239 were all reported as main products


9


Page 10 of 24

when the cells containing H2O additive. To comprehensively identify the product deposited on discharged cathodes, the cathodes discharged with and without H2O were extracted and examined by powder X-ray diffraction (PXRD) and Fourier transform infrared (FT-IR). As shown in Figures 2d and 2e, only Li2O2 forms for a strictly dry electrolyte, however, LiOH, in addition to Li2O2, is also detected for H2O-involved cells. Furthermore, the higher H2O content the electrolyte contained, the larger quantity of LiOH the discharge product formed. The formation of LiOH is speculated as the consequence of the chemical reaction between Li2O2 and H2O, which was previously reported but attributed to different mechanisms.37,40,41 Obviously, H2O, as a protic additive, not only triggers the occurrence of the solution mechanism but also incurs the mixture of Li2O2 and LiOH as products, in stark contrast with strictly dry electrolyte. To further reveal the discharge reaction mechanism of H2O-involved aprotic Li-O2 batteries, we conducted in situ DEMS to investigate the gas consumption on discharge. As shown in Figure 3a, 3c and 3e, O2 is consumed during discharge, and the ratios of electrons to oxygen are all close to 2e-/O2, which indicates two-electron reduction of O2, regardless of the presence of H2O (Table S1, Supporting Information). Combined with the above CVs, SERS, XRD and FT-IR analyses, the reaction mechanism on the discharge of H2Oinvolved Li-O2 batteries is clear that Li2O2 as major discharge product is initially generated via the solution pathway and then dissolves into bulk electrolyte to react with H2O, and therein partly produce LiOH. However, in our galvanostatic discharge-charge experiment, Li2O2 is not able to completely convert into LiOH without any specific catalysts37,38 via the plausible mechanism (Li2O2 + 2H2O ↔ 2LiOH + H2O2),32,34,40 which could be ascribed to the exhaustion of H2O upon lengthy discharge and the very limited solubility of LiOH in H2O-involved organic electrolytes.


10

Page 11 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 3. In situ DEMS while cycling the strictly dry and H2O-containing Li-O2 batteries at current density of 100 mA/g, (a),(b) 0 M H2O; (c),(d) 1 M H2O; (e),(f) 10 M H2O.

On the other hand, the role of H2O and its effect towards recharge are still under dispute. Recently, only Qiao et al.36 have reported that additional H2O generated moderate HO2- species facilitating the cell operated with low overpotentials. Unfortunately, HO2- species was not detected in our work. Besides, other previous reports manifested that LiOH, other than Li2O2, as the exclusive product can also be oxidizeded at low charge potentials in H2O-involved cells with employing specific catalysts.37,38 These debatable results in literatures impel us to scrutinize the effects of H2O on recharge behaviors of batteries. Hence, DEMS was also implemented to in situ monitor gas evolution during recharge. Notably, the charge plateau was significantly reduced from 4.0 V to 3.6 V with increasing the water content to 10 M, as shown in Figure 3b, 3d and 3f.


11


Page 12 of 24

These observations obviously manifest that H2O has a positive effect on reducing polarization. O2 is evolved at a steady rate upon charge, however, except O2, CO2 is also delayed generated. The values of 2.21, 2.51 and 2.78 e-/O2 were obtained for strictly dry, 1 M H2O and 10 M H2O containing electrolytes, respectively, and all values were slightly off ideal 2e-/O2 (Table S2, Supporting Information), which suggested that detrimental parasitic reactions occurred upon recharge. Moreover, the time span of O2 release is shortened and the corresponding quantity of released O2 is reduced with increasing the H2O content (Figure 3 and Table S2, Supporting Information). The above DEMS data on recharge show that H2O additive can greatly reduce charge polarization, and alleviate CO2 release from parasitic reactions at high potentials, furthermore, the cell’s reversibility is slightly destroyed once H2O intrudes in the electrolyte on account of the decreased quantity of O2 evolved. Considering that LiOH partly exists in discharge products with H2O additive (shown in Figure 2d and 2e), we conjecture that LiOH plays a crucial role in enhancing the kinetics of electrochemical oxidation of Li2O2, revealing low charging over-potentials, possibly due to the improved charge transport properties of Li2O2 by LiOH doping. So we measured the ionic and electronic conductivity of both Li2O2 and LiOH by constructing ionically blocking electrodes (see Supporting Information for experimental details and Figures S4 and S5). The results (Table S3, Supporting Information) clearly show that the ionic (σion) and electronic (σeon) conductivity of LiOH were 1.99 × 10-8 S cm-1 and 7.13 × 10-12 S cm-1, respectively, both higher than those of Li2O2 (σion and σeon were 4.03 × 10-10 S cm-1 and 1.25 × 10-12 S cm-1, respectively). Therefore, it is reasonable to attribute the lower charging overpotential to the enhanced conductivity of LiOH on the Li2O2 surface with the aid of H2O.


12

Page 13 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Furthermore, we speculate the reduced quantity of O2 evolved in H2O-involved cells, shown in preceding DEMS study, is attributable to anoxygenic oxidation of LiOH in products. To verify this hypothesis, the electrochemical oxidation of isotope-labelled Li18OH was also interrogated by DEMS, as shown in Figure S6. Surprisingly, neither

18

O2 nor C18O2 gas was detected at

potentials even higher than 4.8 V, except for the C16O2 gas from the decomposition of the carbon electrode or electrolyte. This result verified that LiOH in the product could not contribute to the O2 evolution during recharge, therefore, O2 evolution on charging is solely from the decomposition of Li2O2. Recently, Liu et al.42 also verify that oxidation of LiOH can not release O2 in ruthenium catalyzed Li-O2 battery. Based on the obtained results, the “double-edged” effect of H2O on charging is clear. H2O induces a blend of LiOH and Li2O2, efficiently reducing charging polarization, but slightly sacrificing the reversibility of cells. In conclusion, firstly, by spectroscopic identification of reaction intermediates, we obtain the direct evidence for the hypothesis that H2O can induce Li2O2 formation via a solutionmediated mechanism of ORR, and at a critical H2O content, the discharge product of Li-O2 batteries can form only through the solution-mediated mechanism, even at high overpotential region. Secondly, combined analyses using DEMS studies of H2O-involved Li-O2 batteries and isotope-labelled Li18OH, and direct conductivity measurement of both Li2O2 and LiOH films provide compelling evidence that LiOH, which forms on pre-discharging in H2O-containing electrolytes, can attribute to the lower charging over-potential due to its higher conductivity than that of insulating Li2O2, however, LiOH could not contribute to the O2 evolution upon recharge. Thus, our findings deepen the cognitions of O2 electrochemistry in H2O-involved Li-O2 batteries, highlighting the beneficial effect of H2O as a protic additive on promoting the solution mechanism and hypopolarization on cycling the batteries. Whereas, the addition of H2O might


13


Page 14 of 24

degrade the reversibility of Li-O2 cells. This revealed “double-edged” functions of H2O provide new insights into the trade-offs in selecting protic additives or redox mediators, and impel us to seek applicable soluble additives to fulfill the high performances of aprotic Li-O2 batteries.

ASSOCIATED CONTENT Supporting Information The Supporting Information is available free of charge on the ACS Publications website at http://pubs.acs.org. Materials and experimental details and additional cyclic voltammetry, ICPMS, impedance and DEMS data (PDF) AUTHOR INFORMATION Corresponding Author *E-mail address: [email protected] ORCID Shunchao Ma: 0000-0003-2745-4419 Jiawei Wang: 0000-0002-1847-7267 Jun Huang: 0000-0002-1668-5361 Zhen Zhou: 0000-0003-3232-9903 Zhangquan Peng: 0000-0002-4338-314X Author Contributions ⊥

S. Ma and J. Wang contributed equally to this work. All authors contributed to the design of the

research. S. M. and J. W. performed the experimental measurement and data analysis. S. M. and J. W. conducted the in situ SERS measurements and electrochemical characterizations. S. M.


14

Page 15 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


performed in situ DEMS tests. All authors co-wrote the manuscript. Z. P. supervised the work. All authors discussed the results and commented on the manuscript. Notes The authors declare no competing financial interests.

ACKNOWLEDGMENT The project was supported by the National Natural Science Foundation of China (Grant No. 21605136, 91545129 and 21575135), the “Strategic Priority Research Program” of the CAS (Grant No. XDA09010401), the “Recruitment Program of Global Youth Experts” of China, the National Key Research and Development Program of China (Grant No. 2016YFB0100100), and the Science and Technology Development Program of the Jilin Province (Grant No. 20160414034GH). REFERENCES (1) Abraham, K. M.; Jiang, Z. A Polymer Electrolyte-Based Rechargeable Lithium/oxygen Battery. J. Electrochem. Soc. 1996, 143, 1−5. (2) Girishkumar, G.; McCloskey, B. D.; Luntz, A. C.; Swanson, S.; Wilcke, W. Lithium-Air Battery: Promise and Challenges. J. Phys. Chem. Lett. 2010, 1, 2193−2203. (3) Bruce, P. G.; Freunberger, S. A.; Hardwick, L. J.; Tarascon, J. –M. Li–O2 and Li–S Batteries with High Energy Storage. Nat. Mater. 2012, 11, 19−29. (4) Peng, Z. Q.; Freunberger, S. A.; Chen, Y. H.; Bruce, P. G. A Reversible and Higher-Rate Li– O2 Battery. Science 2012, 337, 563−566. (5) Wang, L.; Zhang, Y.; Liu, Z.; Guo, L.; Peng, Z. Understanding oxygen electrochemistry in aprotic Li–O2 batteries. Green Energy Environ 2017, 2, 186–203.


15


Page 16 of 24

(6) Zhang, X.; Wang, X. G.; Xie, Z.; Zhou, Z. Recent progress in rechargeable alkali metal–air batteries. Green Energy Environ 2016, 1, 4−17. (7) Lu, Y. –C.; Gallant, B. M.; Kwabi, D. G.; Harding, J. R.; Mitchell, R. R.; Whittingham, M. S.; Shao–Horn, Y. (2013). Lithium–oxygen batteries: bridging mechanistic understanding and battery performance. Energy Environ. Sci. 2013, 6, 750−768. (8) Ogasawara, T.; Débart, A.; Holzapfel, M.; Novák, P.; Bruce, P. G. Rechargeable Li2O2 Electrode for Lithium Batteries. J. Am. Chem. Soc. 2006, 128, 1390–1393. (9) Aurbach, D.; McCloskey, B. D.; Nazar, L. F.; Bruce, P. G. Advances in understanding mechanisms underpinning lithium–air batteries. Nat. Energy 2016, 1, 16128. (10) Tian, F.; Radin, M. D.; Siegel, D. J. Enhanced Charge Transport in Amorphous Li2O2. Chem. Mater. 2014, 26, 2952–2959. (11) Gerbig, O.; Merkle, R.; Maier, J. Electron and Ion Transport in Li2O2. Adv. Mater. 2013, 25, 3129–3133. (12) Zhang, X.; Guo, L.; Gan, L.; Zhang, Y.; Wang, J.; Johnson, L. R.; Bruce, P. G. Peng, Z. LiO2: Cryosynthesis and Chemical/Electrochemical Reactivities. J. Phys. Chem. Lett. 2017, 8, 2334−2338. (13) Wandt, J.; Jakes, P.; Granwehr, J.; Gasteiger, H. A.; Eichel, R. −A. Singlet Oxygen Formation during the Charging Process of an Aprotic Lithium–Oxygen Battery. Angew. Chem. 2016, 128, 7006−7009. (14) Luntz, A. C.; McCloskey, B. D. Nonaqueous Li-Air Batteries: A Status Report. Chem. Rev. 2014, 114, 11721−11750. (15) Li, F.; Zhang, T.; Zhou, H. Challenges of non-aqueous Li–O2 batteries: electrolytes, catalysts, and anodes. Energy Environ. Sci. 2013, 6, 1125−1141.


16

Page 17 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(16) Lu, J.; Li, L.; Park, J.-B.; Sun, Y.-K.; Wu, F.; Amine, K. Aprotic and Aqueous Li−O2 Batteries. Chem. Rev. 2014, 114, 5611−5640. (17) Mahne, N.; Fontaine, O.; Thotiyl, M. O.; Wilkening, M.; Freunberger, S. A.; Mechanism and performance of lithium–oxygen batteries–a perspective. Chem. Sci., 2017, 8, 6716−6729. (18) Peng, Z. Q.; Freunberger, S. A.; Hardwick, L. J.; Chen, Y. H.; 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. 2011, 50, 6351−6355. (19) Laoire, C. O.; Mukerjee, S.; Abraham, K. M.; Plichta, E. J.; Hendrickson, M. A. Influence of Nonaqueous Solvents on the Electrochemistry of Oxygen in the Rechargeable lithium−air Battery. J. Phys. Chem. C 2010, 114, 9178−9186. (20) Zhang, Y. L.; Zhang, X. M.; Wang, J. W.; McKee, W. C.; Xu, Y.; Peng, Z. Q. 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. (21) Johnson, L.; Li, C.; Liu, Z.; Chen, Y.; Freunberger, S. A.; 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. (22) 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. (23) Adams, B. D.; Radtke, C.; Black, R.; Trudeau, M. L.; Zaghib, K.; Nazar, L. F. Current density dependence of peroxide formation in the Li–O2 battery and its effect on charge. Nazar, Energy Environ. Sci. 2013, 6, 1772–1778.


17


Page 18 of 24

(24) Wang, J.; Zhang, Y.; Guo, L.; Wang, E.; Peng, Z. Identifying Reactive Sites and Transport Limitations of Oxygen Reactions in Aprotic Lithium–O2 Batteries at the Stage of Sudden Death. Angew. Chem. Int. Ed. 2016, 55, 5201–5205. (25) Luntz, A. C.; Viswanathan, V.; Voss, J.; Varley, J. B.; Nørskov, J. K.; Scheffler, R.; Speidel, A. Tunneling and Polaron Charge Transport through Li2O2 in Li–O2 Batteries. J. Phys. Chem. Lett. 2013, 4, 3494−3499. (26) Zhou, B.; Guo, L.; Zhang, Y.; Wang, J.; Ma, L.; Zhang, W. –H.; Fu, Z.; Peng, Z. A High– Performance Li–O2 Battery with a Strongly Solvating Hexamethylphosphoramide Electrolyte and a LiPON–Protected Lithium Anode. Adv. Mater. 2017, 29, 1701568. (27) Burke, C. M.; Pande, V.; Khetan, A.; Viswanathan, V.; McCloskey, B. D. Enhancing electrochemical intermediate solvation through electrolyte anion selection to increase nonaqueous Li–O2 battery capacity. Proc. Natl. Sci. U. S. A. 2015, 112, 9293–9298. (28) Gao, X.; Chen, Y.; Johnson, L.; Bruce, P. G. Promoting solution phase discharge in Li–O2 batteries containing weakly solvating electrolyte solutions. Nat. Mater. 2016, 15, 882–888. (29) Matsuda, S.; Hashimoto, K.; Nakanishi, S. Efficient Li2O2 Formation via Aprotic Oxygen Reduction Reaction Mediated by Quinone Derivatives. J. Phys. Chem. C. 2014, 118, 18397– 18400. (30) Sun, D.; Shen, Y.; Zhang, W.; Yu, L.; Yi, Z.; Yin, W.; Wang, D.; Huang, Y.; Wang, J.; Wang D.; Goodenough, J. B. A Solution–Phase Bifunctional Catalyst for Lithium–Oxygen Batteries. J. Am. Chem. Soc. 2014, 136, 8941–8946. (31) Lacey, M. J.; Frith, J. T.; Owen, J. R. A redox shuttle to facilitate oxygen reduction in the lithium air battery. Electrochem. Commun. 2013, 26, 74–76.


18

Page 19 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(32) Aetukuri, N. B.; McCloskey, B. D.; García, J. M.; Krupp, L. E.; Viswanathan, V.; Luntz, A. C. Solvating additives drive solution-mediated electrochemistry and enhance toroid growth in non-aqueous Li–O2 batteries. Nat. Chem. 2015, 7, 50−56. (33) Gao, X.; Jovanov, Z. P.; Chen, Y.; Johnson, L. R.; Bruce, P. G. Phenol‐Catalyzed Discharge in the Aprotic Lithium–Oxygen Battery. Angew. Chem. 2017, 129, 6639–6643. (34) Schwenke, K. U.; Metzger, M.; Restle, T.; Piana, M.; Gasteiger, H. A. The Influence of Water and Protons on Li2O2 Crystal Growth in Aprotic Li–O2 Cells. J. Electrochem. Soc. 2015, 162, A573– A584. (35) Kwabi, D. G.; Batcho, T. P.; Feng, S.; Giordano, L.; Thompson, C. V.; Shao-Horn, Y. The effect of water on discharge product growth and chemistry in Li–O2 batteries. Phys. Chem. Chem. Phys. 2016, 18, 24944–24953. (36) Qiao, Y.; Wu, S.; Yi, J.; Sun, Y.; Guo, S.; Yang, S.; He, P.; Zhou, H. From O2− to HO2−: Reducing By–Products and Overpotential in Li–O2 Batteries by Water Addition. Angew. Chem. Int. Ed. 2017, 56, 4960–4964. (37) 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. (38) Li, F.; Wu, S.; Zhang, T.; He, P.; Yamada, A.; Zhou, H. The water catalysis at oxygen cathodes of lithium–oxygen cells. Nat. Commun. 2015, 6, 8843. (39) Guo, Z.; Dong, X.; Yuan, S.; Wang, Y.; Xia, Y. Humidity effect on electrochemical performance of Li–O2 batteries. J. Power Sources, 2014, 264, 1–7. (40) 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.


19


Page 20 of 24

(41) Zhu, Y. G.; Liu, Q.; Rong, Y.; Chen, H.; Yang, J.; Jia, C.; Yu, L. –J; Karton, A.; Ren, Y.; Xu, X.; Adams, S.; Wang Q. Proton enhanced dynamic battery chemistry for aprotic lithium– oxygen batteries. Nat. Commun. 2017, 8, 14308. (42) Liu, T.; Liu, Z.; Kim, G.; Frith, J. T.; Garcia–Araez, N.; Grey, C. P. Understanding LiOH Chemistry in a Ruthenium–Catalyzed Li–O2 Battery. Angew. Chem. Int. Ed. 2017, 56, 16057– 16062.


20

Page 21 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


TOC 50x47mm (300 x 300 DPI)



Figure 1 209x199mm (300 x 300 DPI)


Page 22 of 24

Page 23 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 2 30x23mm (300 x 300 DPI)



Figure 3 49x38mm (300 x 300 DPI)


Page 24 of 24

Unveiling the Complex Effects of H2O on DischargeâRecharge

Recommend Documents

Unveiling the Complex Effects of H2O on DischargeâRecharge