Corrosion Suppression of Aluminum Metal by Optimizing Lithium Salt

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Corrosion suppression of aluminum metal by optimizing lithium salt concentration in solid-state imide saltbased polymer plastic crystal electrolyte membrane Yumei Zhou, Jianchen Hu, Peixin He, Yuhong Zhang, Jingjing Xu, and Xiaodong Wu ACS Appl. Energy Mater., Just Accepted Manuscript • DOI: 10.1021/acsaem.8b01443 • Publication Date (Web): 12 Nov 2018 Downloaded from http://pubs.acs.org on November 13, 2018

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ACS Applied Energy Materials

Corrosion suppression of aluminum metal by optimizing lithium salt concentration in solid-state imide salt-based polymer plastic crystal electrolyte membrane Yumei Zhou,a,b,† Jianchen Hu,c,† Peixin He,a Yuhong Zhang,a,* Jingjing Xu,b,* Xiaodong Wub a Hubei Collaborative Innovation Center for Advanced Organic Chemical Materials, Key Laboratory for the Synthesis and Application of Organic Functional Molecules, Ministry of Education, College of Chemistry and Chemical Engineering, Hubei University, Wuhan 430062, P.R. China b i-Lab, Suzhou Institute of Nano-Tech and Nano-Bionics (SINANO), Chinese Academy of Sciences, 398 Ruo-shui Road, Suzhou Industrial Park, Suzhou 215123, P.R. China c National Engineering Laboratory for Modern Silk, College of Textile and Clothing Engineering,

Research

Center

of

Cooperative

Innovation

for

Functional

Organic/Polymer Material Micro/Nanofabrication, Soochow University, 199 Ren-Ai Road, Suzhou Industrial Park, Suzhou 215123, P.R. China. Corresponding author: Yuhong Zhang: *E-mail: [email protected]; Tel: (+86)-27-88662747 Jingjing Xu: *E-mail: [email protected]; Tel: (+86)-512-62872503

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ABSTRACT: Imide salt-polymer plastic crystal electrolytes (PPCEs) have been demonstrated to be very promising solid-state electrolytes for ambient lithium ion batteries (LIBs). However, anodic Al dissolution at high voltage, due to these salts cannot form an AlF3/LiF passivation film (like LiPF6) on Al surface, limits their application in high-voltage solid-state LIBs. In this work two ambient workable PPCEs

with

different

lithium

bis(trifluoromethanesulfonyl)imide

(LiTFSI)

concentration are designed to investigate anodic Al dissolution suppression in solid-state imide salt-based electrolytes. The anodic Al dissolution is examined by scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). The electrochemical performance is evaluated by solid-state LiCoO2/PPCE/Li4Ti5O12 cells. The results demonstrate anodic Al dissolution is efficiently suppressed and the cell electrochemical performance is greatly elevated by optimizing LiTFSI concentration in PPCEs. The suppression mechanism of Al corrosion in concentrated PPCE is analyzed and suggested. KEYWORDS: anodic Al dissolution, imide salt-based polymer plastic crystal electrolytes, high concentration, high voltage, solid-state lithium ion batteries INTRODUCTION The lithium ion batteries (LIBs) containing liquid carbonate organic electrolytes have been suffering some safety issues such as liquid leakage, flammability and even explosion.1, 2 Replacing the liquid organic electrolytes with solid polymer electrolytes is regarded as an effective solution to these safety issues as solid polymer electrolytes

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show excellent flexibility, processability as well as good interfacial contact with the electrodes.3, 4 However, their lower ionic conductivity at ambient temperature limits their future application in solid-state LIBs. Introducing plastic crystalline succinonitrile (SN) molecules into solid polymer electrolytes can obviously improve their room-temperature ionic conductivity and the obtained polymer plastic crystal electrolytes (named as PPCEs) have been proved to be very promising polymer electrolytes for ambient working solid-state LIBs.5-10 It is well known LiPF6 could readily decompose at 60 oC and easily react with trace water to generate HF,11-13 which not only deteriorates the battery performance, but also is harmful to ecosystems. Imide salts, such as Li[N(CF3SO2)2] (LiTFSI), have been receiving intensive attention as lithium salt candidates due to their good electrochemical/thermal/chemical stability. LiTFSI-based PPCEs have been widely reported and their electrochemical performances are generally evaluated by the cells cycled with the upper limit voltage of 4.2 V vs. Li0 or 2.7 V vs. Li4Ti5O12 (LTO).8, 10, 14, 15

Nevertheless, the stability of current collector is one of important factors for cell

performance.16-19 When using LiTFSI as electrolyte salt, it is unable to passivate Al metal like LiPF6 salt which can provide F- to form a layer of insoluble AlF3 and LiF on Al surface, accordingly the oxidative dissolution issue of Al current collector will become seriously when applying LiTFSI-based PPCE in solid-state LIBs with higher voltage.18,

19

Therefore, solving anodic Al dissolution is very significant for

LiTFSI-based PPCEs to endow their applicability in high-voltage solid-state LIBs. It



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has been demonstrated that the anodic Al dissolution at high voltage can be suppressed by using highly concentrated liquid electrolytes.18, 20, 21 However, anodic Al dissolution at high voltage and its suppression have never been explored in solid-state electrolyte including PPCEs. In this paper, we designed two ambient workable PPCE membranes with different LiTFSI concentrations to investigate anodic Al dissolution and suppression in solid-state imide salt-based electrolytes. The PPCE ionic conductivity was measured by electrochemical impedance spectroscopy (EIS) at 20 oC. The anodic stability was examined using LiCoO2 (LCO)/PPCE/Li4Ti5O12 (LTO) cells by cyclic voltammetry (CV). Anodic Al dissolution was investigated by scanning electron microscope (SEM, Hitachi S4800) equipped with an energy dispersive spectrometer (EDS) detector. The high-voltage electrochemical performance was evaluated by LCO/PPCE/LTO cells with the upper limit voltage of 3.0 V vs. LTO (i.e. 4.5 V vs. Li0). The coordination of Li+ ions to TFSI- anions/SN molecules was tested by Raman microspectroscopy and Fourier Transform infrared (FTIR) spectroscopy. The results manifested comparing with the PPCE with lower LiTFSI concentration, the concentrated PPCE efficiently restrained anodic Al dissolution. The LCO/LTO cell with concentrated PPCE exhibited superior cyclic performance and higher coulombic efficiency than that with lower LiTFSI concentration. The cause of the enhanced electrochemical performance was analyzed and the Al dissolution suppression mechanism was suggested. RESULTS AND DISCUSSION


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Figure 1 Photographs of a representative PPCE membrane on showing the transparency (a) and its flexibility (b) which contained no more than 38 wt% of LiTFSI. (c) Photograph of the PPCE membrane containing 44 wt% of LiTFSI showing uneven surface. (d) EIS spectra of symmetrical SS/PPCE/SS cells with different LiTFSI percentage, which were measured at a frequency range from 1 MHz to 10 Hz with amplitude of 5 mV. (e) Relationship between ambient ionic conductivity and LiTFSI percentage in PPCEs. (f) CV profiles of two LCO/PPCE/LTO cells carried out at 25 oC and 0.2 mV s-1. The inset in (f) revealed PPCE-1 membrane had turned into dark brown black after CV measurement.

To obtain PPCE membranes with high ionic conductivity as well as good flexibility, the percentage of Poly(vinylidene fluoride-hexafluoro propylene) (PVDF-HFP) in PPCEs was selected as 18 wt%. Five PPCE membranes containing a fixed 18 wt% of PVDF-HFP and variable LiTFSI or SN percentage were prepared. The four PPCEs with 12 wt%, 18wt%, 30 wt% and 38 wt% of LiTFSI were uniform and colorless membranes with excellent flexibility whose representative photographs were shown in Figure 1a and Figure 1b. The PPCE with 44 wt% of LiTFSI was an uneven membrane with many particles on its surface (Figure 1c), implying it was unsuitable 5 ACS Paragon Plus Environment


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to be as an electrolyte membrane for solid-state LIBs. The ambient EIS curves of symmetrical stainless steel (SS)/stainless steel (SS) cells with the five PPCE membranes could be seen in Figure 1d and the ambient conductivities () of the five PPCEs were calculated by the equation, σ=

L SR

Where R was the resistance that can be gotten from EIS, L was the thickness of each PPCE, and S was the area of each PPCE film. The relationship between ambient conductivity and LiTFSI percentage in PPCEs could be found in Figure 1e. The results manifested that the ionic conductivities rose firstly and then went down with LiTFSI percentage increase, might because low LiTFSI concentration couldn’t form effective ionic transportation paths in the solid PPCE film, while high LiTFSI concentration highly restrained the ion pair dissociation of LiTFSI salt. The two PPCEs with 12 wt% and 44 wt% of LiTFSI displayed lower ionic conductivity. But the three PPCEs containing 18 wt%, 30 wt% and 38 wt% of LiTFSI exhibited excellent ambient ionic conductivities higher than 1x10-3 S cm-1, which were similar to the value of liquid electrolytes, implying they were very promising polymer electrolytes for ambient workable solid-state LIBs. To study the influence of LiTFSI concentration on anodic Al dissolution at high voltage, two PPCEs with high ambient ionic conductivity as well as apparently different LiTFSI concentrations were selected to carry out the following characterizations. The one with low LiTFSI concentration (18 wt%) was named as PPCE-1, and the other one with high LiTFSI concentration


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(38 wt%) was named as PPCE-2. The anodic stability is important for PPCE application in high-voltage solid-state LIBs. The electrolyte with SN has been proved being unstable when contact with Li metal,10, 22 which was also confirmed by our experiment that the surface of Li metal became black after immersing it in SN solvent for 2 hours at 60 oC, shown in Figure S1. Here the anodic stability of the two PPCEs was evaluated by CV measurement on LCO/PPCE/LTO cells which were carried out from open circuit voltage until 4.0 V vs. LTO (i.e. 5.5 V vs. Li0) at 25 oC and 0.2 mV s-1. From Figure 1f, a strong anodic peak appearing at around 2.5 V vs. LTO (i.e. 4.0 V vs. Li0) was attributed to Co2+/Co4+ oxidation.10, 22 There was another peak emerged at around 3.60 V vs. LTO (or 5.10 V vs. Li0), which might be ascribed to the oxidation of SN or Al current collector. To investigate the attribution of the anodic peak at around 3.60 V, another separate CV experiment was carried out on a LCO/LTO cell with 18 wt% LiTFSI/EC/DMC liquid electrolyte and cellulose separator, shown in Figure S2a. Obviously, the peak at 3.60 V didn’t exist when the electrolyte didn’t contain SN, demonstrating it was exclusively from SN oxidation. Furthermore, the cell with PPCE-1 was disassembled after CV measurement and it could be clearly seen that the colorless and transparent PPCE-1 membrane had turned into dark brown black (the inset in Figure 1f), while the cellulose membrane in LiTFSI/EC/DMC liquid electrolyte was still white (the inset in Figure S2a), further demonstrating the color change of PPCE-1 was from the oxidation of SN. Besides, the anodic peak of Al



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oxidation wasn’t clearly seen in the CV curves because the work electrode (WE) was LCO on the Al current collector and the anodic Al oxidation was covered by the Co2+/Co4+ oxidation. To prove this point, a new CV curve was carried out on Al/LTO cells with 18 wt% LiTFSI/EC/DMC liquid electrolyte, shown in Figure S2b. The result demonstrated when WE was Al metal, the anodic peak of Al oxidation was clearly seen which started from around 2.05 V vs. LTO (~3.55 V vs. Li/Li+) with a much lower strength than Co2+/Co4+ oxidation, demonstrating the anodic Al oxidation was covered by the anodic peak of Co2+/Co4+ oxidation.

Figure 2 SEM images of Al surface (a, b, c), the cumulative charge profiles over time (d) and the surface elements analysis (e, f) after the chronocoulometry measurements of Al current collectors, which were carried out at 3.0 V vs. LTO for 24 h using different Al/LTO cells with PPCE-1, PPCE-2 and a PPCE based on 18 wt% LiPF6.

To investigate clearly the anodic Al dissolution at high voltage, three Al/LTO coin cells with PPCE-1, PPCE-2 and a PPCE membrane containing 18 wt% LiPF6 were charged at 3.0 V vs. LTO for 24 h and subsequently the cells were disassembled to observe the surface of Al electrodes touching the PPCEs. The SEM image in Figure 8 ACS Paragon Plus Environment

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2a revealed many holes were found on the Al surface touching PPCE-1, while there were only a few holes seen on that of PPCE-2 (Figure 2b), and there was no hole on LiPF6-based PPCE (Figure 2c). That meant concentrated PPCE-2 could efficiently suppress anodic Al dissolution, but not fully suppressed like LiPF6-based PPCE. The cumulative charge profiles over time can also represent the extent of anodic Al dissolution in different PPCEs.23 From Figure 2d, concentrated PPCE-2 displayed improved resistance against anodic Al dissolution than diluted PPCE-1 but not as good as LiPF6-based PPCE, which was in agreement with the SEM results. These phenomena were consistent with those references in which anodic Al dissolution in dilute imide-based liquid electrolytes has been proved to be restrained by improving electrolyte concentration.18, 20, 21 During the process of Al anodic dissolution, Al is oxidized to Al3+ cation which will dissolve into the PPCEs. Accordingly, to further prove the suppression of PPCE-2 to Al anodic dissolution, the surface elements of the two PPCEs after chronocoulometry were analyzed by EDS, shown in Figure 2e and 2f. As expected, the peak of Al element in PPCE-1 was stronger than that in PPCE-2, indicating more Al3+ cations dissolved into PPCE-1, further demonstrating anodic Al dissolution was restrained by improving LiTFSI concentration. Besides, elements of C, O, F and S could be seen in the two PPCEs, therein O and S came from LiTFSI and F element was mainly from PVDF-HFP. Higher signal peak of S element was seen in PPCE-2 than PPCE-1 due to PPCE-2 contained higher LiTFSI concentration. To our knowledge, this was the first



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report on anodic Al dissolution and its effective suppression at high voltage in solid-state electrolyte.

Figure 3 Representative galvanostatic charge/discharge voltage profiles in the first cycle and 100th cycle of the LCO/LTO cells with PPCE-1 (a) and with PPCE-2 (b). Cyclic performance (c) and the corresponding coulombic efficiency (d) of the LCO/ LTO cells which were cycled during the voltage range of 1.5-3.0 V at 25 °C and 0.5 C for 100 cycles. The insets in (d) displayed two transparent and colorless PPCE membranes on the blue background, demonstrating SN hasn’t been oxidized during the 100 cycles.

The above characterizations revealed the oxidative decomposition of SN and the anodic Al dissolution were effectively suppressed in higher concentrated PPCE-2, so it was reasonable to believe the PPCE-2 would display superior cyclic stability in high-voltage LIBs. Due to SN can react with Li metal, the SN-based PPCE membrane has been reported to manifest poor cycle life in LCO/Li cells with an upper limit of 4.2 V vs. Li0 but display good electrochemical stability in LCO/LTO cells with an 10 ACS Paragon Plus Environment

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upper cut-off voltage of 2.7 V vs. LTO.5, 10, 14, 15 Here, the electrochemical stability of the two PPCEs was investigated by two LCO/LTO cells which were cycled at 0.5 C for 100 cycles at 25 °C. To investigate the effect of LiTFSI concentration on anodic Al dissolution at high voltage, the upper limit voltage was improved from 2.7 V to 3.0 V vs. LTO (equal to 4.5 V vs. Li0). From the galvanostatic charge/discharge voltage profiles in Figure 3a and Figure 3b, the initial specific charge/discharge capacities were 173.9/152.5 mAh g-1 with a coulombic efficiency of 87.7% for PPCE-1, which were a little higher than the values of PPCE-2 (159.9/139.1 mAh g-1 with a coulombic efficiency of 87.0%) due to a little deteriorated ionic conductivity in PPCE-2. The specific charge/discharge capacities in the 100th cycle were 83.6/82.1 mAh g-1 with a coulombic efficiency of 98.2% for PPCE-1 and 123.9/122.8 mAh g-1 with a coulombic efficiency of 99.1% for PPCE-2. From the cyclic performance in Figure 3c, the capacity retention after 100 cycles was 53.8% for PPCE-1 but it was improved to 90.2% for PPCE-2, demonstrating PPCE-2 exhibited enhanced cyclic stability. Furthermore, the cell coulombic efficiency of PPCE-1 was always lower than that of PPCE-2 except that in the initial three cycles, meaning PPCE-2 exhibited significantly improved reversibility (Figure 3d). It has been confirmed that the oxidation potential of SN was beyond 3.5 V vs. LTO (i.e. 5.0 V vs. Li0) in Figure 1f, so we believed the improved cyclic stability in the range of 1.5-3.0 V did not arise from the oxidation of SN. In order to prove this point, the two LCO/LTO cells were disassembled after 100 cycles and the PPCE membranes were observed. The insets in Figure 3d displayed



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that both PPCE-1 and PPCE-2 still maintained transparent and colorless membranes even if they endured 100 cycles. In view of SN oxidation made the colorless and transparent PPCE become a dark brown black membrane (the inset of Figure 1f), it could be concluded that the oxidative decomposition of SN didn’t happen in the 100 cycles. Hence, the enhanced cyclic performance and reversibility in PPCE-2 were mainly related to the suppression of anodic Al dissolution at high voltage.

Figure 4 Schematic illustrations of anodic Al dissolution behavior in dilute PPCE-1 (a) and concentrated PPCE-2 (b).

The schematic illustration for the suggested suppression mechanism of Al corrosion in the PPCEs was manifested in Figure 4. The surface of Al current collector was covered with a protective Al2O3 layer arising from exposure to air. When charging LCO cathode at high voltage, Al2O3 was corroded to generate Al3+ cation. In PPCE-1 with lower LiTFSI concentration, there were many free SN molecules which would rapidly coordinate to Al3+ cation and led to Al2O3 continuous dissolution. Subsequently, without the protective Al2O3 layer, the underlying Al metal was furtherly corroded and dissolved (Figure 4a), which was similar with Al dissolution 12 ACS Paragon Plus Environment

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process in dilute liquid electrolyte.18, 23 On the contrary, when charging LCO cathode at high voltage in PPCE-2, higher LiTFSI concentration and lower SN concentration made the combination of SN molecules/TFSI- anions and Li+ cations strengthened. That meant free SN and free TFSI- anions were greatly decreased in PPCE-2 and their coordination to Al3+ cations was suppressed, thus the Al dissolution at high voltage was effectively restrained (Figure 4b), which was in accordance with the suppression mechanism of Al corrosion in high concentrated liquid electrolyte.18, 20, 21, 23

Figure 5 (a) Raman spectra of nonpolar S-N-S bond in TFSI- anions and (b) FT-IR spectra of polar C≡N stretching vibration.

To prove the coordination of SN molecules/TFSI- anions to Li+ cations was strengthened as well as free SN and free TFSI- were reduced along with LiTFSI concentration increase and SN concentration decrease in PPCEs, Raman spectra of nonpolar S-N-S bonds in pristine LiTFSI, PPCE-1, PPCE-2 and the PPCE containing 44% of LiTFSI (named as 44% PPCE, which showed uneven surface morphology and the worst ionic conductivity at 20 oC in the five PPCEs) were characterized. Figure 5a displayed the stretching vibrational mode of S-N-S in TFSI- anions. The peak of 13 ACS Paragon Plus Environment


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S-N-S bond appeared at 742 cm-1 in PPCE-1 and gradually shifted to a higher wavenumber along with LiTFSI concentration increase. It emerged at 750 cm-1 in pristine LiTFSI salt. The band at around 740 cm-1 has previously been assigned to free TFSI- anions, the peak at around 745 cm-1 is regarded as contact ion pairs (CIP, TFSIcoordinating to a single Li+ cation), and the 750 cm-1 is ascribed to aggregates (AGGs, TFSI- coordinating to two or more Li+ cations).24, 25 Consequently, the peak shifting to a higher wavenumber revealed the coordination of TFSI- to Li+ cations became stronger and free TFSI- anions were decreased. FTIR spectroscopy is a more effective approach to investigate polar bond. Figure 5b manifested the IR characteristics of C≡N bonds in PPCE-1, PPCE-2 and 44% PPCE. The peak at 2255 cm-1 was ascribed to free nitrile groups, and the peak at 2280 cm-1 belonged to the vibrational frequency of the –C≡N bound to Li+.5,

25

Obviously, the peak at 2255 cm-1 was gradually

weakened and the peak at 2280 cm-1 became much stronger along with LiTFSI concentration rising in PPCEs, implying free SN was decreased and the coordination of SN to Li+ cations was strengthened. These results offered a direct support to our suggested suppression mechanism of anodic Al dissolution. CONCLUSIONS Two solid-state imide salt-based polymer plastic crystal electrolytes (PPCEs) were prepared to investigate the influence of LiTFSI concentration on anodic Al dissolution suppression. The results demonstrated improving LiTFSI concentration in solid-state PPCE efficiently suppressed anodic Al dissolution at high voltage. The solid-state


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LiCoO2/Li4Ti5O12 cell with concentrated PPCE-2 displayed superior cyclic stability and higher coulombic efficiency than that with lowly concentrated PPCE-1. After 100 cycles at 0.5 C and 25 oC, the capacity retention was improved from 53.8% in PPCE-1 to 90.2% in PPCE-2. The strengthened combination between SN molecules/TFSIanions and Li+ ions in concentrated PPCE-2, which restrained the coordination of Al3+ to SN molecules or TFSI- anions, was recommended to be responsible for the suppression of Al corrosion. EXPERIMENTAL SECTION Li[N(CF3SO2)2] (LiTFSI) was purchased from Dong Guan Shanshan Battery Materials Co. Ltd. Poly(vinylidene fluoride-hexafluoro propylene) (PVDF-HFP, Mw=440,000) and succinonitrile (SN) were bought from Sigma-Aldrich Corporation. LiCoO2 (LCO), Li4Ti5O12 (LTO), acetylene black (AB) and Poly(vinylidene fluoride) (PVDF) were purchased from Hefei Kejing Materials Technology Co. Ltd. Other organic solvents were products of Aladdin Co. Ltd. Preparation of the PPCE membranes. LiTFSI, SN and PVDF-HFP were dissolved into acetone according to the mass ratio of 12/70/18, 18/64/18, 30/52/18, 38/44/18 and 44/38/18 in a high-purity Ar filled glove box with the content of water below 5 ppm. The mixtures were stirred magnetically to obtain homogeneous solutions. Then, the PPCE membranes were prepared by tape-casting the solution onto the stainless steel molds with a diameter of 20 mm and kept at ambient temperature for 7 days to make the acetone fully volatilized. Finally, five flexible and self-standing PPCE



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membranes were acquired. Characterization of the PPCE membranes. The ionic conductivities of PPCE films were examined by EIS on symmetrical stainless steel (SS)/PPCE/stainless steel (SS) cells. These symmetrical cells were firstly kept at 20 oC for 30 min to achieve thermal equilibrium, and then they were measured at a frequency range from 1 MHz to 10 Hz with 5 mV of amplitude by Autolab PGSTAT302. CV measurement was carried out to measure the anodic stability of the PPCEs using LCO/PPCE/LTO cells with a scan rate of 0.2 mV s-1 by Autolab PGSTAT302. The anodic Al dissolution was investigated using Al/PPCE/LTO coin cells which were carried out by charged at 3.0 V for 24 h. Then, the morphologies of Al metals and the surface elements of PPCEs were characterized by SEM equipped with an EDS detector. Laser confocal Raman microspectroscopy (LABRAM, HR) and FTIR spectroscopy were used to test the coordination of Li+ ions to TFSI- anions/SN molecules. Fabrication and high-voltage electrochemical performance of LCO/PPCE/ LTO cells. The LCO cathode was prepared by mixing LCO, AB and PVDF with a mass ratio of 8:1:1 followed by casting onto an Al foil current collector by a doctor-blade method and vacuum drying for 24 h at 80 oC. The LTO anode was prepared by the same method with a mass ratio of 7:2:1. The loading densities of LCO and LTO electrodes were 1.0 mg cm-2 and 1.1 mg cm-2, respectively. The capacity ratio of negative to positive electrode (N/P ratio) was around 1.2. The dried electrodes were cut to a diameter of 15 mm, and coin-type cells (CR2025) were assembled by LCO


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cathode, PPCE as electrolyte and separator, and LTO anode in a high-purity Ar filled glove box. The galvanostatical charge/discharge cycles were performed in the voltage range of 1.5-3.0 V by a Neware battery testing equipment with a current density of 0.5 C (1 C=150 mAh g-1) at 25 oC. ASSOCIATED CONTENT Supporting Information. The supporting information are available free of charge.

Photographs of Li metal before and after immersing it in SN solvent at 60 oC for 2 hours. CV profiles of a LCO/LTO cell and an Al/LTO cell with 18 wt% LiTFSI/EC/EMC liquid electrolyte and a cellulose separator. AUTHOR INFORMATION Corresponding Author *E-mail: [email protected]; *E-mail: [email protected] ORCID Jingjing Xu: 0000-0002-1050-7660 Author Contributions The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript. †These authors contributed equally. Notes



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The authors declare no competing financial interest. ACKNOWLEDGMENT We gratefully acknowledge the financial support provided by the Natural Science Foundation of China [grant number: 21503265, 51603135, 21473241] and the Project of Science and Technology Innovation Team of Outstanding Young and Middle-aged Scientists, Department of Education of Hubei Province (T201801). REFERENCES (1) Xu, J. J.; Hu, Y. Y.; Liu, T.; Wu, X. D. Improvement of Cycle Stability for High-voltage Lithium-Ion Batteries by In-situ Growth of SEI Film on Cathode. Nano Energy 2014, 5, 67-73. (2) Xu, J. J.; Xia, Q. B.; Chen, F. Y.; Liu, T.; Li, L.; Cheng, X. Y.; Lu, W.; Wu, X. D. Facilely Solving Cathode/Electrolyte Interfacial Issue for High-voltage Lithium Ion Batteries by Constructing an Effective Solid Electrolyte Interface Film. Electrochim. Acta 2016, 191, 687-694. (3) Meyer, W. H. Polymer Electrolytes for Lithium-Ion Batteries. Adv. Mater. 1998, 10, 439-448. (4) Goodenough, J. B.; Singh, P. Review-Solid Electrolytes in Rechargeable Electrochemical Cells. J. Electrochem. Soc. 2015, 162, A2387-A2392. (5) Kwon, T.; Choi, I.; Park, M. J. Highly Conductive Solid-State Hybrid Electrolytes Operating at Subzero Temperatures. ACS Appl. Mater. Interfaces 2017, 9, 24250-24258.


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Kimura,

K.;

Polycarbonate-Based

Motomatsu, Solid

J.;

Polymer

Tominaga, Electrolytes

Y.

Highly Having

Concentrated Extraordinary

Electrochemical Stability. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 2442-2447.



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(25) Yamada, Y.; Furukawa, K.; Sodeyama, K.; Kikuchi, K.; Yaegashi, M.; Tateyama, Y.; Yamada, A. Unusual Stability of Acetonitrile-Based Superconcentrated Electrolytes for Fast-Charging Lithium-Ion Batteries. J. Am. Chem. Soc. 2014, 136, 5039-5046.

Table of Contents graphic:


Corrosion Suppression of Aluminum Metal by Optimizing Lithium Salt

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