Polyiodide-Shuttle Restricting Polymer Cathode for Rechargeable

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Polyiodide-Shuttle Restricting Polymer Cathode for Rechargeable Lithium/Iodine Battery with Ultra Long Cycle Life Zhen Meng, Huajun Tian, Shunlong Zhang, Xufeng Yan, Hangjun Ying, Wei He, Chu Liang, Wenkui Zhang, Xianhua Hou, and Wei-Qiang Han ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.8b03212 • Publication Date (Web): 08 May 2018 Downloaded from http://pubs.acs.org on May 8, 2018

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ACS Applied Materials & Interfaces

Polyiodide-Shuttle

Restricting

Polymer

Cathode

for

Rechargeable Lithium/Iodine Battery with Ultra Long Cycle Life Zhen Meng,†§ Huajun Tian,†* Shunlong Zhang,†Xufeng Yan,†Hangjun Ying,† Wei He,† Chu Liang,⊥ Wenkui Zhang,⊥ Xianhua Hou,II Wei-Qiang Han, †‡*

†

Ningbo Institute of Material Technology and Engineering

Chinese Academy of Sciences Ningbo 315201, P. R. China ‡

School of Materials Science and Engineering

Zhejiang University, Hangzhou 310027, P. R. China §

University of Chinese Academy of Sciences

Beijing 100049, P.R. China ⊥

Zhejiang University of Technology, College of Materials Science & Engineering

Hangzhou 310014, P. R. China II

School of Physics and Telecommunication Engineering, South China Normal

University Guangzhou 510006, P.R. China *

Corresponding authors.

E-mail: [email protected] E-mail: [email protected]

S-1 ACS Paragon Plus Environment

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ABSTRACT: Rechargeable lithium/iodine (Li/I2) batteries have attracted much attention due to their high gravimetric/volumetric energy densities, natural abundance and low cost. However, problems of the system, such as highly unstable iodine species under high temperature, their subsequent dissolution in electrolyte and continually reacting with lithium anode prevent the practical use of rechargeable Li/I2 cells.

A

polymer-iodine composite

(polyvinylpyrrolidone-iodine) with

high

thermostability is employed as cathode material in rechargeable Li/I2 battery with an organic electrolyte. Due to the chemical interaction between polyvinylpyrrolidone (PVP) and polyiodide, most of the polyiodide in the cathode could be effectively trapped during charging/discharging. In-situ Raman observation revealed the evolution of iodine species in this system could be controlled during the process of I ↔ I ↔ I . Herein, the Li/I2 battery delivered a high discharge capacity of 278 mAh g-1 at 0.2 C and exhibited a very low capacity decay rate of 0.019 % per cycle for prolonged 1100 charge/discharge cycles at 2C. More importantly, a high areal capacity of 4.1 mAh cm-2 was achieved for the electrode with high iodine loading of 21.2 mg cm-2. This work may inspire new approach to design the Li/I2 (or Li/polyiodide) system with long cycle life. Keywords: Lithium/iodine battery, polyvinlpyrrolidone-iodine, chemical interaction, cycle performance, shuttle effect 1. INTRODUCTION Recently, iodine composites have been reported to be remarkably effective at sustaining long-life cycling in Li/Na/Zn/Mg batteries.1-7 Among these systems, lithium/iodine (Li/I2) battery has been studied widely.4-5,

8-9

Compared with the

traditional lithium ion battery, the lithium/iodine (Li/I2) battery could exhibit a reasonable average operation voltage (2.9 V) and a potential high energy density (580


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Wh kg-1). Meanwhile, iodine is an abundant, low cost cathode material with a high volumetric energy density of 1040 mAh cm-3 and a specific capacity of 211 mAh g-1, which make the Li/I2 full cell a highly promising prospect of commercialization application in energy storage and conversion, such as electric vehicles and large-scale grid storage.4-5 Even though the solid-phase primary (single-use) lithium-iodine (Li/I2) battery, with high reliability and low self-discharge rate, has been used in cardiac pacemakers,10 it could only discharge at very low current density and could not be used as a rechargeable cell. Recently, some research processes on the rechargeable Li/I2 battery have been achieved.4-5, 8, 11-13 However, the obstacles which such devices face still need to be significantly solved. Firstly, different from that in the solid-phase primary (single-use) Li/I2 battery, both the iodine and polyiodide formed during charge/discharge process dissolve easily into the organic electrolyte, which uncontrollably diffuse to the anode and react with metal Li, resulting in severe selfdischarge and low Coulombic efficiency. This is similar with the “shuttle effect” in lithium-sulfur (Li/S) battery chemistry. Secondly, even though iodine is solid at room temperature, its high subliming tendency due to the high vapor pressure heightens the difficulties during the preparation of cathode electrode. To address these issues, some attention has been paid to different kinds of porous carbon materials as iodine matrixes. Ye et al. prepared an iodine-conductive carbon black (CCB) composite via a thermal treatment method.5 The active iodine was loaded in the pores of the CCB. During the repeatedly charge/discharge process, the diffusion of iodine species was decreased by the physical adsorption of the pores in the CCB. Chen et al. loaded the iodine in a porous carbon cloth via a “solutionadsorption” process.4 This cathode possesses advantages as follows: (i) the carbon cloth promises superior conductivity; (ii) the porous structure has acceptable physical



adsorbability, which could restrain the sublimation of iodine; (iii) the iodine/carbon cloth cathode without binder and conductive additives saves the cost of the batteries. The above mentioned methods on retarding dissolution and/or diffusion of iodine and polyiodide were mainly controlled by the relatively week physical confinement, which needs to be further improved. Especially, carbon, being non polar in nature, is incompetent to adsorb polar iodine species such as I and I−. Lu et al. employed a free-standing, flexible nitrogen and phosphorus co-doped hierarchically porous graphitic carbon as iodine host.1 They found that heteroatoms could enhance the adsorbability of the carbon to iodine. When used as cathode material in Na/Li-I2 half/full cell, it all exhibited enhanced electrochemical performance. Pan et al. demonstrated a highly reversible aqueous zinc−iodine battery using encapsulated iodine in microporous carbon as the cathode material by controlling solid−liquid conversion reactions.2 DFT simulation suggested that the active materials were preferentially adsorbed onto carbon rather than dissolved in water solvents due to their stronger interaction with the carbon surface, leading to negligible self-discharge behavior and long cycle life. As inspired by the Li/S battery chemistry, a more efficient approach to trap polysulfides is to utilize the chemical interaction between the host material and lithium polysulfides,14-17 and the more targeted approach to suppress the dissolution of iodine species could be to employ the chemical interaction between the host material and iodine species. In this work, we firstly report an exceptional stable rechargeable Li/I2 battery through effectively controlling polyiodide shuttle by a chemical interaction PVP-I2 cathode and optimizing the electrolyte chemistry. Different from previous reports, the PVP-I2 cathode could largely suppress the dissolution of iodine species into the organic electrolyte by the


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chemical interaction between the iodine species and the PVP polymer, which enhanced the electrochemical performance. Polyvinylpyrrolidone, a polymer which is physiologically acceptable to animals and humans, has the ability to tie up iodine to form Polyvinylpyrrolidone-iodine complex.

The

polyvinylpyrrolidone-iodine

complex

is

known

as

polyvinylpyrrolidone-iodine or povidone-iodine (PVP-I2).18 In the past few decades, this product has served as an iodophor and become the universally preferred iodine antiseptic instead of iodine. Herein, we employed PVP-I2 as the cathode material for rechargeable Li/I2 battery with liquid organic electrolyte since not only does PVP-I2 retain the chemical nature of iodine,18-19 but also superior to iodine, PVP-I2 has some other valuable characteristics. After combining with PVP, the vapor pressure of iodine is significantly reduced,19 resulting in thermostable complex. Thus, the sublimation of iodine is restrained effectively. Furthermore, the chemical interaction between PVP and iodine species retards dissolution of iodine species into the organic electrolyte by anchoring them in the cathode, resulting in negligible self-discharge reaction. Compared with pure iodine, PVP-I2 is more environmentally friendly. The reaction mechanism of Li/I2 battery with PVP-I2 as cathode has been investigated by in-situ Raman analysis. Besides the Raman signals of I , which has also been reported in the iodine/nanoporous carbon cathode,4 obvious signals of I were detected. As far as the authors are aware, no Raman signal of I was reported in rechargeable Li/I2 battery with liquid electrolyte till the moment. This work provides a new insight to design the Li/I2 battery, and also inspires the development of robust Li/polyiodide system with higher energy density. 2. EXPERIMENTAL SECTIONS 2.1. Sample preparation



2.1.1. Preparation of PVP-I2 cathodes. The PVP-I2 we used was a commercial product (Sigma-aldrich) with 13 wt% of iodine (the iodine content was measured by ion chromatography). 70 wt% of commercial PVP-I2, 27.5 wt% of Ketjen Black (KB) and 2.5 wt% of graphene (G) were mixed by ball milling under an argon atmosphere. The mixture was grinded with binder PTFE (at 6:1 weight ratio of mixture: PTFE) and then rolled into thin piece. Then the thin piece was punched into electrodes with area of around 0.6-0.8 cm2. The iodine loading was 2 mg cm-2. For the PVP-I2 cells with high iodine loading, the iodine loading is 4.1-10.4 mg cm-2. 2.1.2. Preparation of PVP-I2 with high iodine content (PVP-I2-H) and PVP-I2-H cathodes. The PVP-I2-H were prepared according to a method reported previously.20 1.5 g of powdered iodine was added to 10 ml of 1 M PVP solution in methanol. Then the methanol was evaporated and the product was treated under vacuum at room temperature for about 1 week to remove the extra iodine. The iodine content in this product is 30 wt%, which was calculated according to the following formula: Mass fraction of iodine =

( ) –( ) ( )

× 100 wt%; m(PVP-I2-H) and m(PVP)

represent the mass of PVP-I2-H prepared and the mass of PVP used respectively.The preparation of PVP-I2-H cathodes were the same with that of PVP-I2 cathodes except PVP-I2 was replaced by PVP-I2-H. The preparation of PVP-I2-H cathodes was same with that of PVP-I2 cathodes except PVP-I2 was replaced by PVP-I2-H. The iodine loading is 3.8-21.2 mg cm-2. 2.1.3. Preparation of pure I2 cathodes. The preparation of pure I2 cathodes was similar with that of the PVP-I2 cathodes. The iodine loading in the electrode was similar with that of the PVP-I2 cathode. 2.2. Electrochemical tests


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CR2032 coin cells were assembled in an Ar-filled glove box with Li-metal anode and PVP-I2 (or PVP-I2-H) cathodes. The electrolytes were 1M LiN(CF3SO2)2 (LiTFSI) in a 1:1 v/v mixture of 1,3-dioxolane/1,2-dimethoxyethane (DOL/DME) containing 1 wt% of LiNO3. The separator was Celgard 2300 separator. For the SIS electrolytes experiments, the concentrations of LITFSI in the electrolytes were increased to 3M and 7M. The amount of the electrolyte used in the cells were all 80 µL. Galvanostatic discharge/charge tests on the Li/I2 cells were performed by cycling between 2.0 - 3.6 V or between 2.5 - 3.4 V. 2.3. Material characterization The Raman spectra were obtained with a Renishaw inVia Reflex Raman spectrometer. To get the Raman spectra of I and I , laser excitation at 532 nm was used. To get the ex-situ Raman spectra of C=O in the PVP, laser excitation at 633 nm was employed. Since polyiodides were sensitive to oxygen and humidity, the cathodes charged and discharged to different potentials were all sealed in quartz tubes in Ar atmosphere to make sure that the ex-situ Raman spectrum reflects the real state of the cathode. X-ray photoelectron spectroscopy (XPS) spectra were measured by an Axis Ultra DLD imaging photoelectron spectrometer. Thermogravimetric analysis (TGA) was performed by a Pyris Diamond analyzer under nitrogen flow with a heating rate of 5 ℃ min-1. Scanning electron microscope (SEM) measurements and energy dispersive X-ray spectroscopy (EDS) were taken using FEI Quanta FEG 250 field emission microscopy. Ion chromatography was measured with a Thremo ICS1100 Ion Chromatograph.

3. RESULTS AND DISCUSSION



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Molecular characteristics of the PVP-I2 have been shown in Figure S1. In the X-ray diffraction (XRD) pattern of the PVP-I2 (Figure S1a), the absence of iodine crystal peaks implies the intimate interaction between PVP and iodine. Raman spectrum of PVP-I2 (Figure S1b) shows a strong peak between 120-110 cm-1 which is related to the symmetric stretching mode of I , indicating that iodine is mainly tied to PVP via the formation of polyiodides. The chemical interaction

significantly

enhances

the

thermostability

of

iodine.18

Thermogravimetric analysis (TGA) (Figure S1c) indicates most of the iodine is released above 200 ℃. This is considerably different from the TGA curves of pure iodine and pure I2/KB/G (Figure S1c and d), which exhibits much weight loss before 100 oC and 150 oC, respectively. More importantly, compared with the highly soluble pure iodine in the electrolyte, the dissolution of iodine was largely suppressed by the interaction between PVP and iodine (Figure S1e). The electrolyte with pure I2 was dark brown, indicating that large amount of iodine species dissolved into the electrolyte. In contrast, the electrolyte with PVP-I2 was transparent light brown even standing for 10 days, proving the beneficial PVP-I2 interaction. The scanning electron microscopy (SEM) image and the corresponding energy dispersive X-ray (EDX) elemental mapping of iodine in PVP-I2 are shown in Figure S2. The signal of iodine is uniformly matched with the PVP-I2 region, indicating the homogeneous distribution of iodine. To prepare the cathode electrodes, PVP-I2 and conductive additives (Ketjen Black and graphene) were mixed by ball milling, and the elemental mappings presented the uniform distribution of I, C and N after ball milling (Figure S2). Then the PTFE was added and the mixture was made into thin pieces, which were used directly as electrodes. This thin piece showed a wellS-8 ACS Paragon Plus Environment

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knit structure (Figure S3). For comparison, the electrode with just conductive additives and PTFE was also made. However, with the absence of PVP-I2, it was very difficult for the conductive additives and PTFE to integrate well with each other (Figure S3). This might be due to the adhesive and binding power PVP processes,21 which ensures the close combination of the materials in the electrode. The thickness of the electrode pieces with different iodine loading were also shown in Figure S3 (e-i). For the PVP-I2 electrode with iodine loading of 2 mg cm-2, its thickness was 75µm. For the PVP-I2-H electrodes with iodine loading of 3.8 mg cm-2, 8.0 mg cm-2, 10.2 mg cm-2 and 21.2 mg cm-2, the thickness were 50 µm, 86 µm, 96 µm and 220 µm, respectively. The TGA curves and N2 adsorption−desorption isotherms of these electrodes (Figure S4) exhibited no obvious differences, indicating the same chemical and physical properties of the electrodes with different thicknesses. Figure 1a shows representative galvanostatic discharge/charge voltage profiles of the initial two cycles of the Li/I2 cell with PVP-I2 as cathode at 0.2C (1C = 211 mA g-1). For the previous Li/I2 batteries with iodine/carbon cathodes reported, two reduction plateaus at around 3.3 and 2.9 V appeared in the first discharge process.4-5 These represent the reduction of I2 to LiI3 and further to LiI. The PVP-I2 cathode, however, showed only one distinct plateau at 2.9 V with the absence of another plateau at around 3.3 V in the first discharge



Figure 1. (a) Discharge and charge voltage profiles of the first two cycles of Li/I2 batteries with PVP-I2 as cathode at 0.2C. (b) Discharge curves of the first cycles after standing different time at 0.2C. (c) Discharge and charge curves of the initial cycle and the discharge curve of the second cycle of an in-situ Raman cell with PVP-I2 as cathode. (d) In-situ Raman analysis corresponding to the marked points in (c). (e) The evolution of iodine species in the PVP-I2 cathode.

process. This denotes that the original iodine species in PVP-I2 is bound to PVP frameworks by forming I , which is consistent with the chemical formula (Figure S9) of PVP-I2. The charge capacity of the second cycle was a little higher than that of the first, which might be attributed to the activation process in the first cycle. After standing for different time before discharging, the cells showed similar initial discharge curves at 0.2 C (Figure 1b). The initial discharge capacities of the three cathodes after standing 12 h, 24 h and 72 h were


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228.4, 225.8, 222.0 mA h g-1, respectively. No obvious capacity decay could be observed with the standing time increasing. Due to the chemical interaction between iodine species and PVP, most of the I was trapped in the cathode, so the polyiodides diffusion was largely suppressed, leading to negligible self-discharge phenomenon at open circuit.4 This also proves that the absence of the plateau at around 3.3 V in the first discharge process is not caused by the self-discharging since negligible self-discharge could be detected. In our experiment, 12 h, 24 h or 72 h was enough for the electrolyte to fully infiltrate into the electrode. So no obvious polarization differences could be detected. The self-discharge rate of the cell at room temperature was shown in Figure S5, after standing for 240 h, the cell showed a low self-discharge rate of 0.0063 % h-1, which was comparable to the lithiumsulfur battery reported.22-24. In the charge process, LiI was oxidized to LiI3 at around 3.1 V and further to higher valence iodine species above 3.4 V.4-5 After the first discharge/charge cycle, two discharge plateaus appeared at around 3.4 V and 2.9 V ascribed to the formation of LiI3 and LiI, respectively.25 The capacity contributions of these two processes were 50.1 mAh g-1 and 228.3 mAh g-1. To gain insight into the evolution of iodine species in the rechargeable Li/I2 battery with PVP-I2 as cathode during discharge/charge processes, we performed in-situ Raman spectroscopic analysis. In-situ Raman spectra obtained from the initial discharge/charge cycle and the discharge process of the second cycle are shown in Figure 1c and 1d. The region below 200 cm-1 was selected for research since this was the region of interest for polyiodide species.26-29 Before discharging, the strong peak between 120-110 cm-1 related to symmetric stretching mode I could be detected. At the discharge process,



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the Raman intensity of I peak decayed gradually until it is disappeared, indicating that only one transformation from LiI3 to LiI occurred. This is consistent with that the initial discharge curve displayed only one single plateau. The reduction of LiI3 to LiI was also proved by X-ray photoelectron spectroscopy (XPS) analysis (Figure S6). After discharging, the I 3d5/2 and I 3d3/2 peaks in the I 3d XPS spectrum shifted down to 618.1 eV and 629.6 eV, respectively, indicating the formation of LiI.30 During the charging process, the intensity of I peak increased at the first voltage plateau and then decreased in the following charging process, corresponding to the reaction of LiI to LiI3 and then the oxidation of I . A peak between 170 and 160 cm-1 related to the linear symmetric stretching mode of I emerged during charging,26,

29, 31

which

implied that different reactions and different polyiodides generated in the charging process. In the charging voltage plateau at around 3.1 V, the intensity of I peak increased with most of I being oxidized to I . Then a part of I was further oxidized to longer I above 3.4 V with the intensity of I weakened. At the final charging state (3.6 V), the Raman signals of I could still be detected, meaning that I coexisted with I in the cathode. In the discharging process of the second cycle, the reversed reaction of the charging process was detected. The peak of I increased with that of I decreased and then both of them disappeared at around 3.2 V and 2.8 V, respectively, indicating that I was first reduced to I and further to I . The evolution of iodine species in the cell with PVP-I2 as cathode is I ↔ I ↔ I (Figure 1e). Nevertheless, the tendency of iodine to form polyiodides such as I is highly dependent on the cation, while lithium is reluctant to form lithium polyiodides with longer polyiodides.32 Therefore the appearance of I in the cathode could S-12 ACS Paragon Plus Environment

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be attributed to the chemical bonding between PVP and iodine, which enhance the stability of I in the organic electrolyte. Cyclic voltammograms (CVs) of the PVP-I2 cathode was also measured to further illustrate the coexistence of I and I (Figure S7). When the potential range was 2.0-3.6 V, two cathodic peaks at 3.40 and 2.85 V can be identified, indicating the two-step reduction mechanism. The capacity contributions of the two processes calculated based on the two cathodic peaks were 19.2 mA h g-1 (peak at 3.40 V) and 198.0 mA h g-1 (peak at 2.85 V) (Figure S7b and e). In the oxidation process, only one complete anodic peak at 3.1 V (I to I ) could be observed. If the potential range extended to 2.0−3.8 V, another complete anodic peak appeared at 3.6 V (Figure S7c). According to our in-situ Raman spectra, this peak was related to the conversion from I to I . This means that I could not be oxidized totally in the cell with PVP-I2 as cathode at the cut-off voltage of 3.6 V. It should be noted that the high voltage might catalyze the side reactions with electrolyte.33-34 The CV curves of the electrolyte (1M LiTFSI in a 1:1 v/v mixture of DOL/DME containing 1 wt% of LiNO3) with lithium foil and aluminum foil as anode and cathode between 2.0 – 4.0 V were also measured (Figure S7d) in the same condition. No obvious complete oxidation peak could be observed at 3.6 V, indicating the appearance of the anodic peak at 3.6 V was not induced by the decomposition of the electrolyte. To evaluate the electrochemical performance of the PVP-I2 cathode, CR2032 coin cells were assembled with lithium foils as anodes. Figure 2a and 2b presented the rate performance of the cell at various C-rates. With increasing current density, both the discharge voltage plateaus and the discharge capacity decreased gradually due to the higher ohmic and kinetic overvoltage at higher



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current densities.35 From 0.2 C to 5C, only a modest drop in capacity from 273 to 186 mAh g-1 was observed. The high capacity in such high current density (5C) suggested efficient kinetics.15 The average reversible discharge capacities were 273, 245, 230, 214 and 183 mAh g-1 at current densities of 0.2 C, 0.5 C, 1 C, 2 C and 5 C, respectively. When the current density was gradually decreased to 0.2 C, the capacities were largely recoverd, which indicates the robustness and stability of the PVP-I2 cathode. It should be mentioned that the theoretical capacity of I2 is 211 mAh g-1. The higher capacity of the PVP-I2 cathode is ascribed to that the conductive additive (Ketjen Black and graphene) and PVP also contributes capacity (Figure S8). The capacity from the Ketjen Black and graphene is capacitive. The high extra capacity which results from the host material is a common phenomenon in the reports of Li/I 2 battery (Table S1). 4-5,

9

The capacitive

characteristic of the Ketjen Black and graphene is very good at high-rate charge/discharge. However, even at high discharge rate of 5C, obvious voltage plateau could also be observed, which suggested efficient transformation of iodine


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Figure 2. (a) Discharging/charging voltage profiles at 0.2C, 0.5C, 1C, 2C and 5C. (b) Rate performance. (c) Cycling performance at 0.2C, 0.5C, 1C and 2C. (d) Digital photos of one rechargeable Li/I2 coin cell with PVP-I2 as cathode lighting 1 and 38 red LEDs at 2.90 V. (g and h) Long –term cycle stability of the cells with PVP-I2 as cathodes at (e) 0.5C, (f) 2C.

species. Meanwhile, the synergistic effect between the capacitive characteristic of the conductive additive and redox capacity of active iodine ensured high energy and power performance for the rechargeable Li/I2 battery, which was also an effective S-15 ACS Paragon Plus Environment


strategy in consistent with a previous report.5 Figure 2c showed the cycle performance of the cells at different current densities. The cell delivered a discharge capacity of 278 mAh g-1 at the second cycle at 0.2 C. After 100 cycles, a discharge capacity of 244 mAh g-1 still remained. At higher current densities (0.5C, 1C and 2C), the cells all represented good cycle stability. In addition, even at 0.2 C, the Coulombic efficiency of the cell was nearly all above 97.5 %, indicating the iodine shuttle had been suppressed effectively. To better evaluate the PVP-I2 cathode for high power supply, one coin cell with 1.3 mg of iodine was used as power for light-emitting diode (LED) (nominal voltage is 2 V, nominal power is 30 mW) (Figure 2d). The coin cell could power one LED efficiently at 2.9 V, meaning that the instantaneous current was 7.96 A g-1, corresponding to the C-rate of 38 C. More strikingly, the coin cell could easily power 38 LEDs. These results directly revealed the excellent highpower discharge performance of the electrode. Long-term cycling stabilities of the cells at 0.5 C and 2 C were displayed in Figure 2e and 2f. After an activated process, the cell exhibited a discharge capacity of 247 mAh g-1 and then 233 mAh g-1 at 0.5 C. After 300 cycles, it still maintanied a reversible discharge capacity of 226 mAh g-1. When cycled at 2 C, a high reversible discharge capacity of 190.6 mAh g-1 still remained after 1100 cycles. The decay rate were 0.028 % and 0.019 % for the cells cycled at 0.5 C and 2 C, respectively. In addition, the Coulombic efficiency of these cells were all above 98.0 %. Owing to the thermal stability of PVP-I2, the cell could still work at 50 ℃. For instance, after 100 cycles, a discharge capacity of 222.6 mAh g-1 was still remained (Figure S9).


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In order to further elucidate the improved electrochemical performance of the PVP-I2 cathode, we carried out in-situ visual–electrochemical experiments since the strong color of I2 and polyiodides in the electrolyte could be used to probe their interaction with the cathode surface, similar to Li/S cells.15 As shown in Figure 3a and 3c, the electrolyte in the cell with PVP-I2 as cathode

Figure 3. Visual confirmation of iodine species entrapment at different dischargeg/charge states and the schematic of iodine species distribution in cell. (a) and (c) I2 as cathode and (b) and (d) PVP-I2 as cathode (the iodine loading in each of these two electrodes was 8 mg, the purple, brown and silver-gray balls represent I2, polyiodides and lithium ions, respectively), (e) Raman spectra of PVP, PVP-I2 and the ex-situ Raman spectra of the PVP-I2 cathode at different discharge (3.5, 3.1, 2.8, 2.0V) and charge (2.9, 3.2, 3.6 V) stages in the second cycle.

was bright yellow due to the dissolution of a small amount of iodine. For comparison, the cell using pure I2/Ketjen Black/graphene cathode (pure I2 cathode) with the same iodine loading was also assembled. The electrolyte in the pure I2 cell became dark brown quickly during the discharging process, indicating that huge amount of iodine species diffused out of the cathode and dissolved into the electrolyte. Even at the end of discharging (2.0 V), the electrolyte was still dark brown, suggesting lots of iodine species still remained in solution. In contrast, the bright yellow electrolyte in the PVP-I2 cell showed S-17 ACS Paragon Plus Environment


almost no change throughout the discharge/charge cycling (Figure 3b and 3d). The cycle stability of the PVP-I2 cathode at 0.2C in the in-situ visual– electrochemical experiment was shown in Figure S10a. After 22 cycles, it still exhibited a discharge capacity of 203.1 mA h g-1. More importantly, after suffering a capacity fading over the initial 5 cycles, the cathode exhibited little capacity loss. These provided the visual evidence of that iodine species could be effectively trapped by PVP. The morphology and the element composition of the cathode in CR2032 coin cell at different discharge/charge states were obtained by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) analysis, which showed no significant morphological change (Figure S10b-d) and similar iodine concentration (Table S2). All of these results revealed that most of the iodine species were tightly trapped in the cathode during charging and discharging. To further confirm the beneficial PVP-I2 interaction and prove that this interaction worked not only for the first discharge process, but also for all of the discharge/charge processes, Raman spectra of PVP, PVP-I2 and ex-situ Raman spectra of the PVP-I2 cathode at different discharge (3.5, 3.1, 2.8, 2.0 V) and charge (2.9, 3.2, 3.6 V) stages in the second cycle between 1600-1750 cm-1 were analyzed (Figure 3e). Before the Raman spectroscopic analysis was carried out, all the samples were washed with DME to remove the residual lithium salt. Since polyiodides were sensitive to oxygen and humidity, the cathodes charged and discharged to different potentials were all sealed in quartz tubes in Ar atmosphere to make sure that the ex-situ Raman spectrum reflects the real state of the cathode. The peak of PVP centered at 1663 cm-1 is assigned to the stretching of C=O band from carbonyl group. For the PVP-I2, this peak is positively shifted to 1676 cm-


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1

. On one hand, the iodine molecule could be adhered to the PVP through the

hydrogen bridge involving the carbonyl groups of PVP (Figure S11).20, 36 On the other hand, the iodine could also interact with PVP through the nitrogen lone pair in PVP.37 The synergistic effect above weakened the electrondonating ability of N to C=O, leading to upward shift in the carbonyl band position.38 In the ex-situ Raman spectra of the PVP-I2 cathode at different discharge (3.5, 3.1, 2.8, 2.0 V) and charge (2.9, 3.2, 3.6 V) stages in the second cycle, the peak positions were as follow. PVP: 1663.1 cm-1, PVP-I2: 1677.3 cm-1, 3.5 V: 1678.9 cm-1, 3.1 V: 1677.6 cm-1, 2.8 V: 1676.3 cm-1, 2.0 V: 1676.8 cm-1, 2.9 V: 1676.9 cm-1, 3.2 V: 1676.7 cm-1, 3.6 V: 1678.8 cm-1. Compared with that of PVP, all of the peaks of the stretching of C=O showed upward shift for the PVP-I2 cathode, indicating the interaction between PVP and iodine species still existed in the following discharge/charge processes. It should be noted that to avoid interference, all the cathode electrodes for the ex-Raman analysis were prepared by directly dispersing PVP-I2 powder on a commercial carbon cloth with no C=O group. The easily dissolved iodine species (I2 and polyiodide) in the electrolyte shuttled between cathode and anode, which severely corrode Li metal and destroy the solid electrolyte interface (SEI) layer on the Li metal, leading to low Coulombic efficiency.5, 39-40 Figure S12a and b showed the SEM images of the Li foil anodes after cycling in the in-situ visual–electrochemical experiment with pure I2 and PVP-I2 as cathodes. The surface of the Li metal with pure I2 as cathodes became very rough while that with PVP-I2 as cathodes remained reletively smooth. The micro-morphology of the Li foil anode after 20 cycles in the coin cell with PVPI2 as cathode was also analyzed. Compared with that of the fresh lithium metal anode (Figure S12c and d), the surface of the lithium metal after 20 cycles became rough



(Figure S12e and f), but no obvious Li dendrites could be observed, indicating the lithium metal anode was stable during the cycling in the cell with PVP-I2 as cathode. The coin cell with pure I2 cathode was also assembled. After two discharge/charge cycles, however, it could not be charged to 3.6 V (Figure S13). For the cell with PVP-I2 as cathode, even though PVP is capable of anchoring most of iodine species, the iodine shuttle could not be suppressed completely due to the small amount of iodine dissolving into the electrolyte. So the addition of 1 wt% LiNO3 in the electrolyte was necessary since it benefited the formation of passive film on the surface of Li anode (Figure S14), which would protect the Li metal and improve the Coulombic efficiency of the cell.4, 41

To further control the polyiodide shuttle effect and improve the Coulombic

efficiency of PVP-I2 cell, the “solvent-in-salt” (SIS) electrolyte was also employed. It could not only protect the lithium anode against the formation of lithium dendrites42 but also inhibit the dissolution of the iodine species (Figure S15a). After 100 discharge/charge cycles, the cell with 1M LITFSI electrolyte exhibited Coulombic efficiency of 97.9 %. For the cell with 3M and 7M LITFSI electrolytes, the Coulombic efficiency reached 99.3 % and 99.6 %, respectively (Figure S15b and c), indicating the effective suppression of polyiodide shuttle. But due to relatively higher viscosity of the 3M and 7M LITFSI electrolytes compared with 1M LITFSI electrolyte, the polarization of the cells with 3M and 7M LITFSI electrolytes became larger. Except the concentration of the salt in the electrolyte had impact on polyiodide-suppressing, the electrolyte volume could also affect the electrochemical performance of the cells. The electrochemical performances of the Li-I2 cells with different electrolyte volumes were shown in Figure S16. When the electrolyte volumes were 120, 80,


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60 and 20 µL, the corresponding discharge capacities of the second cycles were 236.6, 247.4, 252.1 and 214.8 mA h g-1, respectively. After 40 cycles, the discharge capacities were 211.9, 233.1, 239.6 and 215.7 mA h g-1, respectively (Figure S16a and b). The average Coulombic efficiencies of the cells with 120, 80, 60 and 20 µL of electrolyte were around 98.2%, 98.9%, 99.2% and 100.0% (Figure S16d). The amount of the dissolved iodine species would be reduced with less electrolyte employed, similar with that of the Li-S batteries

43-44

,

which would benefit the precipitation and dissolution equilibrium of the iodine species and suppress the polyiodides shuttle. As a result, the higher Coulombic efficiencies, discharge capacities and capacities retention could be achieved. However, when the electrolyte volume was too small, such as 20 µL, full infiltration of the electrolyte to the cathode electrode would become difficult. The poor wetting induced an obviously decreased discharge capacity. This was why the discharge capacity of the cell with 20 µL of electrolyte was lower than that of the cell with 60 µL of electrolyte. In the four cells, the one with 60 µL of electrolyte exhibited the highest discharge capacity and the one with 20 µL of electrolyte showed the highest average Coulombic efficiency and capacity retention. Figure S16 proved that by varying the volume of the electrolyte, the iodine species shuttle could be further suppressed and the electrochemical performances of the Li-I2 batteries could be imporved. The generation of a small amount of dissolved iodine species is one of the reasons that caused the shuttle effect.5 If the charging process of the cell terminates without I appeared, I would be the single polyiodide present in the electrolyte. In this case, the iodine shuttle would be also suppressed. According to our in-situ Raman and cyclic voltammetry analyses, I was



mainly generated above 3.4 V. So the evolution of iodine species in the cell could be controlled easily by changing the voltage window. The in-situ Raman spectra also showed that the peak of I disappeared below 2.5 V during discharging (k and π points in Figure 1c, k and π Raman spectra in Figure 1d), which implied that the conversion from I to I had finished below 2.5 V. The other capacity below 2.5 V should result from the Ketjen Black and graphene. So, to suppress the iodind shuttle at the same time to reduce the capacity originating from the Ketjen Black and graphene, the voltage window of 2.5-3.4 V was chosen. The electrochemical performances of the cells with PVP-I2 as cathode between 2.5-3.4 V were evaluated. During discharging/charging, only the reversible redox reaction of I ↔ I occurred (Figure S17 and S18). When cycled at 0.2 C and 0.5 C (Figure S17), the cells all exhibited high Coulombic efficiencies of around 99.9 %, implying the iodine shuttle had been further suppressed. The discharge capacity of cell cycled at 0.5 C was 125.4 mAh g-1 in the initial discharging process and stabilized to > 114 mAh g-1 after 430 cycles. The capacity decay was as low as 0.021 % per cycle. Achieving high active material loading in the electrode is critical for highareal capacity.45 Thick PVP-I2 electrodes with different iodine loading were also prepared. As shown in Figure S19, an areal discharge capacity of 1.2 mAh cm-2 was achieved at 0.2 C for the 4.8 mg cm-2 electrode, which increased to 1.5 mAh cm-2 for the 10.4 mg cm-2 electrode. However, the iodine content in the commericial PVP-I2 we used is only 13 wt%, which hinders the achievement of higher iodine loading in the electrode. One of the advantages of PVP-I2 material is that the iodine content in this composite could be altered and improved easily through changing the preparation process.18 In order to further


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increase the iodine loading in the electrodes, we successfully prepared PVP-I2 composite with higher iodine content (denoted as PVP-I2-H and the iodine content is 30 wt%) and used it as the cathode material. Even though this percentage (30 wt %) is not high enough for Li/I2 battery with high energy density, it is higher than some reports of iodine/carbon cathode (Table S3). Further work on increasing the iodine content of polymer-iodine cathode for higher energy density of the full cell is ongoing. XRD pattern and TGA curve indicated iodine effectively bound to PVP (Figure S20) in the PVP-I2-H composite. The iodine

Figure 4. (a) Cycling stability of the cell with 3.8 mg cm-2 iodine loading. (b) Cycling stability with different iodine loads. (c) Discharge/charge voltage profiles of the second cycles. (d) Comparison of areal capacity.

loading in the electrodes with PVP-I2-H as cathode varied from 3.8 to 21.2 mg cm-2. The cycle performance of the cell with 3.8 mg cm-2 of iodine is displayed in Figure 4a, where the cell exhibited stable cycling. In the second cycle, a discharge capacity of 219 mAh g-1 was achieved. After 90 cycles, it still S-23 ACS Paragon Plus Environment


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maintained a discharge capacity of 203 mAh g-1. Negligible discharge capacity reduction and variation in the voltage polarization was observed with the iodine loading increasing (Figure 4b and 4c). As a result, an areal discharge capacity of 2.2 mAh cm-2 was achieved at 0.2 C for the electrode with iodine loading of 10.2 mg cm-2, which increased to 4.1 mAh cm-2 for the electrode with iodine loading of 21.2 mg cm-2 (Figure 4d). Table S4 summarizes the electrochemical performances of different structures in Li/I2 battery. Our Li/I2 cells exhibit the best ultralong cycle performance than others reported.4-6, 8, 11-13, 46. Compared with other I2/carbon cathodes,4-5,

46

PVP-I2 cathode has much better capacity

retention. Furthermore, the preparation of our Li/I2 cells is simpler than lithiumiodine flow batteries.8, 11-12 4. CONCLUSIONS In summary, for the first time, we employ the PVP-I2 as cathode for rechargeable Li/I2 battery with a commercial liquid electrolyte and a “solvent-in-salt”-type electrolyte. Polyiodides effectively bound to PVP via the chemical interaction, which largely improved the thermal stability of iodine-based cathode. During charging and discharging process, PVP could highly trap polyiodides, and immensely restrained the dissolution of iodine species into the electrolyte, which results in suppressing the shuttling. As a result, the PVP-I2 cathode exhibits exceptional cycling stability (1100 cycles, 2C, 190.6 mAh g-1). In the respect of practical application, the economic and abundant properties of PVP and iodine and the excelent electrochemical performance of the PVP-I2 cathode make it a promising candidate for the power source of the longrange electric vehicles and large-scale grid storage.4-5,

9, 46

In the respect of

fundamental research, we find the chemical interaction between PVP and iodine species could suppress the dissolution of iodine species in the electrolyte. The in-situ


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Raman analysis also revealed that the evolution of iodine species in the cell could be controlled through the process of I ↔ I ↔ I . Moreover, by using the SIS electrolytes and/or reducing the discharge/charge voltage range, the Coulombic efficiency of the cell was further improved (99.9%), indicating that the polyiodide/iodide redox could be effectively tuned by optimizing the cathode and the electrolyte chemistry. Therefore, this work may provide us a novel insight in designing high-performance Li/I2 and Li/polyiodide system with the exceptional stability. ASSOCIATED CONTENT Supporting information Experimental details, physical and chemical characteristic of PVP-I2, SEM images of PVP-I2, PVP-I2 cathodes and lithium metal anode, electrochemical performance, XPS spectra, dissolution tests, tables to show percent of capacity originate from host material in some previous reports, element composition of the cathodes at different discharging/charging states, the comparison of iodine content between our work and previous reports, the electrochemical performances of Li/I2 batteries with different structures. AUTHOR INFORMATION Corresponding Author E-mail: [email protected] E-mail: [email protected] Notes The authors declare no competing financial interest. ACKNOWLEDGEMENTS



The authors are grateful for the financial support by the National Natural Science Foundation of China (Grant No. 51504234 and No. 51371186), Zhejiang Provincial Natural Science Foundation of China (Grant No. LY16E040001), the “Strategic Priority Research Program” of the Chinese Project Academy of Science (Grant No. XDA09010201), the Ningbo 3315 International Team of Advanced Energy Storage Materials, Zhejiang Province Key Science and Technology Innovation Team (Grant No. 2013TD16), the Natural Science Foundation of Ningbo (Grant No. 2015A610252). REFERENCES (1) Lu, K.; Hu, Z.; Ma, J.; Ma, H.; Dai, L.; Zhang, J., A Rechargeable IodineCarbon Battery That Exploits Ion Intercalation and Iodine Redox Chemistry. Nat.

Commun. 2017, 8, 527. (2) Pan, H.; Li, B.; Mei, D.; Nie, Z.; Shao, Y.; Li, G.; Li, X. S.; Han, K. S.; Mueller, K. T.; Sprenkle, V.; Liu, J., Controlling Solid–Liquid Conversion Reactions for a Highly Reversible Aqueous Zinc–Iodine Battery. ACS Energy Letters 2017, 2, 2674-2680. (3) Tian, H.; Gao, T.; Li, X.; Wang, X.; Luo, C.; Fan, X.; Yang, C.; Suo, L.; Ma, Z.; Han, W.; Wang, C., High Power Rechargeable Magnesium/Iodine Battery Chemistry. Nat. Commun. 2017, 8, 14083. (4) Zhao, Q.; Lu, Y.; Zhu, Z.; Tao, Z.; Chen, J., Rechargeable Lithium-Iodine Batteries with Iodine/Nanoporous Carbon Cathode. Nano Lett. 2015, 15, 5982-5987. (5) Wang, Y. L.; Sun, Q. L.; Zhao, Q. Q.; Cao, J. S.; Ye, S. H., Rechargeable Lithium/Iodine Battery with Superior High-Rate Capability by Using Iodine-Carbon Composite as Cathode. Energ Environ. Sci. 2011, 4, 3947-3950.


Page 26 of 32

Page 27 of 32 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


(6) Weng, G.-M.; Li, Z.; Cong, G.; Zhou, Y.; Lu, Y.-C., Unlocking the Capacity of Iodide for High-Energy-Density Zinc/Polyiodide and Lithium/Polyiodide Redox Flow Batteries. Energ Environ. Sci. 2017, 10, 735-741. (7) Li, B.; Nie, Z.; Vijayakumar, M.; Li, G.; Liu, J.; Sprenkle, V.; Wang, W., Ambipolar Zinc-Polyiodide Electrolyte for a High-Energy Density Aqueous Redox Flow Battery. Nat. Commun. 2015, 6, 6303. (8) Zhao, Y.; Wang, L.; Byon, H. R., High-Performance Rechargeable LithiumIodine Batteries Using Triiodide/Iodide Redox Couples in an Aqueous Cathode. Nat.

Commun. 2013, 4, 1896. (9) Li, K.; Lin, B.; Li, Q.; Wang, H.; Zhang, S.; Deng, C., Anchoring Iodine to NDoped Hollow Carbon Fold-Hemisphere: Toward a Fast and Stable Cathode for Rechargeable Lithium–Iodine Batteries. ACS Appl. Mater. Inter 2017, 9, 2050820518. (10) Schmidt, C. L.; Skarstad, P. M., Development of an Equivalent-Circuit Model for the Lithium/Iodine Battery. J. Power. Sources 1997, 65, 121-128. (11) Zhao, Y.; Hong, M.; Mercier, N. B.; Yu, G.; Choi, H. C.; Byon, H. R., A 3.5 V Lithium-Iodine Hybrid Redox Battery with Vertically Aligned Carbon Nanotube Current Collector. Nano Lett. 2014, 14, 1085-1092. (12) Zhao, Y.; Byon, H. R., High-Performance Lithium-Iodine Flow Battery. Adv.

Energy Mater. 2013, 3, 1630-1635. (13) Liu, F.-C.; Liu, W.-M.; Zhan, M.-H.; Fu, Z.-W.; Li, H., An All Solid-State Rechargeable Lithium-Iodine Thin Film Battery Using LiI(3-Hydroxypropionitrile)2 as an I-ion Electrolyte. Energ Environ. Sci. 2011, 4, 1261-1264.



(14) Pang, Q.; Kundu, D.; Cuisinier, M.; Nazar, L. F., Surface-Enhanced Redox Chemistry of Polysulphides on a Metallic and Polar Host for Lithium-Sulphur Batteries. Nat. Commun. 2014, 5, 4759. (15) Liang, X.; Hart, C.; Pang, Q.; Garsuch, A.; Weiss, T.; Nazar, L. F., A Highly Efficient Polysulfide Mediator for Lithium–Sulfur Batteries. Nat. Commun. 2015, 6, 5682. (16) Seh, Z. W.; Wang, H.; Hsu, P.-C.; Zhang, Q.; Li, W.; Zheng, G.; Yao, H.; Cui, Y., Facile Synthesis of Li2S-Polypyrrole Composite Structures for High-Performance Li2S Cathodes. Energ Environ. Sci. 2014, 7, 672-676. (17)Wang, X. L.; Li, G.; Li, J. D.; Zhang, Y. N.; Wook, A.; Yu, A. P.; Chen, Z. W., Structural and Chemical Synergistic Encapsulation of Polysulfides Enables UltralongLife Lithium-Sulfur Batteries. Energ Environ. Sci. 2016, 9, 2533-2538. (18) Siggia, S., The Chemistry of Polyvinylpyrrolidone-Iodine. J. Am. Pharm.

Assoc. 1957, 46, 201-204. (19) Gershenfeld, L., Povidone-Iodine as a Topical Antiseptic. Am. J. Surg. 1957,

94, 938-939. (20) Schenck, H.-U.; Simak, P.; Haedicke, E., Structure of PolyvinylpyrrolidoneIodine (Povidone-Iodine). J. Pharm. Sci. 1979, 68, 1505-1509. (21) Bühler, V., Polyvinylpyrrolidone-Excipients for Pharmaceuticals. Springer 2005. (22) Xu, W.-T.; Peng, H.-J.; Huang, J.-Q.; Zhao, C.-Z.; Cheng, X.-B.; Zhang, Q., Towards Stable Lithium–Sulfur Batteries with a Low Self-Discharge Rate: Ion Diffusion Modulation and Anode Protection. ChemSusChem 2015, 8, 2892-2901.


Page 28 of 32

Page 29 of 32 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


(23) Ryu, H. S.; Ahn, H. J.; Kim, K. W.; Ahn, J. H.; Cho, K. K.; Nam, T. H., SelfDischarge Characteristics of Lithium/Sulfur Batteries Using Tegdme Liquid Electrolyte. Electrochim. Acta 2006, 52, 1563-1566. (24) Hart, C. J.; Cuisinier, M.; Liang, X.; Kundu, D.; Garsuch, A.; Nazar, L. F., Rational Design of Sulphur Host Materials for Li-S Batteries: Correlating Lithium Polysulphide Adsorptivity and Self-Discharge Capacity Loss. Chem. Commun. 2015,

51, 2308-2311. (25) Behl, W. K.; Chin, D. T., Electrochemical Overcharge Protection of Rechargeable Lithium Batteries: I . Kinetics of Iodide/Tri ‐ Iodide/Iodine Redox Reactions on Platinum in Solutions. J. Electrochem. Soc. 1988, 135, 16-21. (26) Jung, N.; Crowther, A. C.; Kim, N.; Kim, P.; Brus, L., Raman Enhancement on Graphene: Adsorbed and Intercalated Molecular Species. ACS Nano 2010, 4, 7005-7013. (27) Stangar, U. L.; Orel, B.; Vuk, A. S.; Sagon, G.; Colomban, P.; Stathatos, E.; Lianos, P., In Situ Resonance Raman Microspectroscopy of a Solid-State DyeSensitized Photoelectrochemical Cell. J. Electrochem. Soc. 2002, 149, E413-E423. (28) Yourey, W.; Weinstein, L.; Amatucci, G. G., Structure and Charge Transport of Polyiodide Networks for Electrolytically in-Situ Formed Batteries. Solid State

Ionics 2011, 204–205, 80-86. (29) Sharp, S. B.; Gellene, G. I., Ab Initio Calculations of the Ground Electronic States of Polyiodide Anions. J. Phys. Chem. A 1997, 101, 2192-2197. (30) Moulder, J. F.; Stickle, W. F.; Sobol, P. E.; Bomben, K. D., Handbook of XRay Photoelectron Spectroscopy. Physical Electronics, Inc. 1995. (31) Mohanambe, L.; Vasudevan, S., Insertion of Iodine in a Functionalized Inorganic Layered Solid. Inorg. Chem. 2004, 43, 6421-6425.



(32) Nour, E. M.; Chen, L. H.; Laane, J., Far-Infrared and Raman-Spectroscopic Studies of Polyiodides. J Phys Chem. 1986, 90, 2841-2846. (33)Geronov, Y.; Puresheva, B.; Moshtev, R. V.; Zlatilova, P.; Kosev, T.; Stoynov, Z.; Pistoia, G.; Pasquali, M., Rechargeable Compact Li Cells with LiXCr0.9V0.1S2 and Li1+XV3O8 Cathodes and Ether‐Based Electrolytes. J. Electrochem. Soc. 1990, 137, 3338-3344. (34) Xu, K., Nonaqueous Liquid Electrolytes for Lithium-Based Rechargeable Batteries. Chem. Rev. 2004, 104, 4303-4418. (35) Qiu, Y.; Li, W.; Zhao, W.; Li, G.; Hou, Y.; Liu, M.; Zhou, L.; Ye, F.; Li, H.; Wei, Z.; Yang, S.; Duan, W.; Ye, Y.; Guo, J.; Zhang, Y., High-Rate, Ultralong CycleLife Lithium/Sulfur Batteries Enabled by Nitrogen-Doped Graphene. Nano Lett. 2014,

14, 4821-4827. (36) Moulay, S., Molecular Iodine/Polymer Complexes. J. Poly. Eng. 2013, 33, 389-443. (37) Hugo, W. B.; Newton, J. M., The Solubility of Iodine in Aqueous Solutions of Non-Ionic Surface-Active Agents. J. Pharm. Pharmacol. 1963, 15, 731-741. (38) Taylor, L. S.; Zografi, G., Spectroscopic Characterization of Interactions between PVP and Indomethacin in Amorphous Molecular Dispersions. Pharm. Res. 1997, 14, 1691-1698. (39) Behl, W. K.; Chin, D. T., Electrochemical Overcharge Protection of Rechargeable Lithium Batteries: Ii . Effect of Lithium Iodide‐Iodine Additives on the Behavior of Lithium Electrode in Solutions. J. Electrochem. Soc. 1988, 135, 21-25. (40) Yan, C.; Cheng, X.-B.; Zhao, C.-Z.; Huang, J.-Q.; Yang, S.-T.; Zhang, Q., Lithium Metal Protection through in-Situ Formed Solid Electrolyte Interphase in


Page 30 of 32

Page 31 of 32 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


Lithium-Sulfur Batteries: The Role of Polysulfides on Lithium Anode. J. Power.

Sources 2016, 327, 212-220. (41) Aurbach, D.; Pollak, E.; Elazari, R.; Salitra, G.; Kelley, C. S.; Affinito, J., On the Surface Chemical Aspects of Very High Energy Density, Rechargeable Li–Sulfur Batteries. J. Electrochem. Soc. 2009, 156, A694-A702. (42)

Suo, L.; Hu, Y.-S.; Li, H.; Armand, M.; Chen, L., A New Class of

Solvent-in-Salt Electrolyte for High-Energy Rechargeable Metallic Lithium Batteries.

Nat. Commun. 2013, 4, 1481. (43)

Cheng, X.-B.; Huang, J.-Q.; Peng, H.-J.; Nie, J.-Q.; Liu, X.-Y.; Zhang, Q.;

Wei, F., Polysulfide Shuttle Control: Towards a Lithium-Sulfur Battery with Superior Capacity Performance up to 1000 Cycles by Matching the Sulfur/Electrolyte Loading.

J. Power. Sources 2014, 253, 263-268. (44)

Zhang, S., Improved Cyclability of Liquid Electrolyte Lithium/Sulfur Batteries

by Optimizing Electrolyte/Sulfur Ratio. Energies 2012, 5 (12), 5190. (45) Pang, Q.; Nazar, L. F., Long-Life and High-Areal-Capacity Li-S Batteries Enabled by a Light-Weight Polar Host with Intrinsic Polysulfide Adsorption. ACS

Nano 2016, 10, 4111-4118. (46) Su, Z.; Tong, C.-J.; He, D.-Q.; Lai, C.; Liu, L.-M.; Wang, C.; Xi, K., UltraSmall B2O3 Nanocrystals Grown in Situ on Highly Porous Carbon Microtubes for Lithium-Iodine and Lithium-Sulfur Batteries. J. Mater. Chem. A 2016, 4, 8541-8547.



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Polyiodide-Shuttle Restricting Polymer Cathode for Rechargeable

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