Ionic Conduction in Composite Polymer Electrolytes: Case of PEO:Ga

10 Dec 2018 - By dispersing Li6.25Ga0.25La3Zr2O12 (Ga-LLZO) nanoparticles in ..... the PEO:Ga-LLZO composite is suitable for high-voltage all-solid-st...
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Cite This: ACS Appl. Mater. Interfaces 2019, 11, 784−791

Ionic Conduction in Composite Polymer Electrolytes: Case of PEO:Ga-LLZO Composites Zhuo Li,†,‡ He-Ming Huang,†,‡ Jia-Kun Zhu,§ Jian-Fang Wu,‡ Hui Yang,*,§ Lu Wei,*,‡ and Xin Guo*,‡ ‡

School of Materials Science and Engineering and §Department of Mechanics, Huazhong University of Science and Technology, Wuhan 430074, P.R. China

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S Supporting Information *

ABSTRACT: By dispersing Li6.25Ga0.25La3Zr2O12 (Ga-LLZO) nanoparticles in poly(ethylene oxide) (PEO) matrix, PEO:Ga-LLZO composite polymer electrolytes are synthesized. The PEO: Ga-LLZO composite with 16 vol % Ga-LLZO nanoparticles shows a conductivity of 7.2 × 10−5 S cm−1 at 30 °C, about 4 orders of magnitude higher than the conductivity of PEO. The enhancement of the ionic conductivity is closely related to the space charge region (∼3 nm) formed at the interface between the PEO matrix and the Ga-LLZO nanoparticles. The space charge region is observed by transmission electron microscope (TEM) and corroborated by the phase-field simulation. Using the random resistor model, the lithium-ion transport in the composite polymer electrolyte is simulated by the Monte Carlo simulation, demonstrating that the enhanced ionic conductivity can be ascribed to the ionic conduction in the space charge regions and the percolation of the space charge regions. KEYWORDS: composite polymer electrolyte, ionic conductivity, space charge region, phase-field simulation, percolation, Monte Carlo simulation

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INTRODUCTION Rechargeable lithium-ion batteries with increased energy density are widely used in electric vehicles and portable electronic devices.1 However, commercial lithium-ion batteries suffer from a major safety problem due to the flammability of organic liquid electrolytes.2 All-solid-state batteries, in which solid electrolytes are used, are considered to be an effective solution to the safety problem. In addition to the better safety, all-solid-state batteries also possess a high energy density, long cycling life, and good reliability.3−5 The commonly used solid electrolytes in all-solid-state batteries are ceramic and polymer electrolytes. Ceramic electrolytes, such as Li0.33La0.557TiO3 (LLTO),6 Li7La3Zr2O12 (LLZO),7−9 Li1.3Al0.3Ti1.7(PO4)3 (LATP),10 and Li10GeP2S12 (LGPS),11 usually have high lithium-ion conductivities (>1 × 10−3 S cm−1 at room temperature),12 wide electrochemical window (>5 V),8,13,14 and good thermal stability (ceramics can withstand temperatures >1000 °C). However, they are brittle, and the huge interface impedance between the electrolyte and electrodes is also a major disadvantage.15−17 In contrast, polymer electrolytes, such as poly(ethylene oxide) (PEO),18,19 polyacrylonitrile (PAN), 20 poly(propylene carbonate) (PPC),21 and poly(vinylene carbonate) (PVCA),22 are flexible and lightweight and the interface resistance can be comparatively small.23,24 Unfortunately, the lithium-ion conductivity of polymer electrolytes is usually low (e.g., 10−6 to 10−8 S cm−1 at room temperature),25 the ionic transference number is small (16 vol % (Figure 1c). Because the conductivity of PEO is on the order of 10−8 S cm−1 (Figure 1c), the conductivity of the bond C (σC) should be much lower than that of the bond A (σA). Using a random resistor network, the ionic conduction in the composite with the special feature of a modified conductivity in the space charge regions is simulated. For a very small p, ∑ is governed by the conductivity of PEO (σC), as shown in Figure 5a. At a concentration where a percolation path of the bond A (σA) is formed for the first time (Figure 5b), the high space charge conductivity becomes dominant, and ∑ increases strongly. By further increasing p, the conductivity ∑ first passes through a maximum and then decreases to a low value at a concentration p′′C, where all the conducting paths are about to be disrupted (Figure 5c). The computational details of the Monte Carlo simulation are given in Figure S12. The results of the Monte Carlo simulation for the relation ∑−p are plotted in Figure 6; the stimulation results are in excellent agreement with our experimentally data. Therefore, the enhanced conductivity of the PEO:Ga-LLZO composite can be ascribed to the fast ionic conduction in the space charge regions, in conjunction with the percolation effect. The percolation of the space charge regions can be successfully applied not only to understand the ionic conduction in the composite, but also to strategically optimize the conductivity. One key parameter to enhance the ionic conductivity is the specific contact area between Ga-LLZO and PEO; decreasing the size of the Ga-LLZO nanoparticles is an effective way to get a larger contact area. Another key parameter is the distribution of the Ga-LLZO nanoparticles (characterized by the percolation efficiency); structure inhomogeneity, such as

= 0 ns. When the Ga-LLZO nanoparticle contacts with PEO matrix, the driving force that stems from the interfacial chemical potential drives lithium ions at regular Ga-LLZO lattice sites to migrate to surface sites, leading to the aggregation of positively charged ions on the surfaces and negatively charged vacancies behind in the lattice (t = 150 ns). With the migration process proceeding further, the system finally reaches at a new equilibrium state (t = 300 ns), leaving a high concentration of lithium ions and a low concentration of vacancies in the surface layer of the Ga-LLZO nanoparticle. As shown in Figure 4b, c, at the equilibrium state, the lithium-ion and vacancy concentrations reach a minimum and a maximum at ∼2 nm away from the Ga-LLZO/PEO interface, respectively. The corresponding dynamic processes are exhibited in Movie S2. In addition, the formation of the space charge region in the system with two Ga-LLZO nanoparticles is provided in Figure S9, Figure S10, Movie S3, and Movie S4. These results uncover that a continuous pathway of the space charge regions can be formed, when the generated space charge regions in individual nanoparticles are connected to each other, as illustrated in Figure 4d. The space charge region has two effects: first, the ionic conductivity is influenced by changing the defect concentration in the region;44 second, it provides a new kinetic pathway for the ionic conduction. Notably, a highly conductive region surrounding an isolated particle barely affects the ionic conductivity; however, if continuous paths are formed (i.e., the situation above the percolation threshold), the contribution of the space charge region to the ionic conductivity is significant. Therefore, in the PEO:Ga-LLZO composite, when the Ga-LLZO content exceeds the percolation threshold value, the formed continuous pathway of the space charge regions can be treated as the fast channel for Li+ ion transportation, as illustrated in Figure 4d. To describe the influence of the Ga-LLZO content on the ion transport in the PEO:Ga-LLZO composite, the random resistor model for the two-phase mixture is used to elaborate the particular role of the space charge conduction, and the Monte Carlo simulation is used to determine the ionic conductivity, ∑, as a function of the concentration, p, of the conductive phase.53,62 In the random resistor model, a cubic space is used to study the two-phase mixture. The unit cubes, representing the dispersed conductive Ga-LLZO particles (α), randomly occupy the space with probability p, while the remaining is the PEO phase (β). The bonds connecting two neighboring sites are identified with electrical resistors, of which are distinguished for three types, as defined in Figure 5. 788

DOI: 10.1021/acsami.8b17279 ACS Appl. Mater. Interfaces 2019, 11, 784−791

Research Article

ACS Applied Materials & Interfaces

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Movie S3 (AVI) Movie S4 (AVI)

AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected] (X.G.). *E-mail: [email protected] (H.Y.). *E-mail: [email protected] (L.W.). ORCID

Hui Yang: 0000-0002-2628-4676 Xin Guo: 0000-0003-1546-8119

Figure 6. Comparison of the ionic conductivity data obtained from the Monte Carlo simulation with those acquired via the experimental measurement for the PEO:Ga-LLZO composite.

Author Contributions †

Z.L. and H.-M.H. contributed equally to this work.

Author Contributions

particle agglomeration and porosity, must be avoided in the composite. Combined the flexibility of PEO with the high ionic conductivity and excellent stability of Ga-LLZO, the PEO:Ga-LLZO composite shows an enormous potential in all-solid-state batteries. The electrochemical window greater than 4.6 V (Figure S13) and the excellent stability against metallic lithium (Figure S14) suggest that the PEO:Ga-LLZO composite is suitable for high-voltage all-solid-state batteries using metallic Li anode. Additionally, operating at 60 °C, the solid-state battery LiFePO4/PEO:Ga-LLZO/Li shows a discharge capacity of 145 mAh g−1 at 0.1 C (Figure S15).

X.G. acquired the funding and supervised the project; X.G. and Z.L. conceived the idea and designed the experiments; Z.L., J.F.W., and L.W. conducted the experiments; Z.L. and H.-M.H. did the Monte Carlo simulation; J.-K.Z. and H.Y. did the phase-field simulation; X.G., Z.L., and H.Y. wrote the manuscript. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work is supported by the National Natural Science Foundation of China (Grant 51672096) and the fund of the State Key Laboratory of Solidification Processing in NWPU (Grant SKLSP201710). H.Y. acknowledges the National 1000 Talents Program of China tenable at the Huazhong University of Science and Technology (HUST), China.

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CONCLUSIONS The enhanced ionic conductivity of the PEO:Ga-LLZO composite polymer electrolyte can be ascribed to the fast ionic conduction in the space charge regions at the interfaces of the PEO matrix and the Ga-LLZO nanoparticles. When the space charge regions and the phase distribution meet the demand of forming the percolation threshold, the percolation effect takes effect, and continuous fast conduction pathways are formed; as a result, the ionic conductivity increases significantly. The mechanistic understanding of the ionic conduction paves the way to the further optimization and targeted design of the composite polymer electrolyte. Moreover, owing to the high ionic conductivity, the electrochemical window greater than 4.6 V and the excellent stability against metallic lithium, the PEO:Ga-LLZO composite polymer electrolyte opens up the opportunity for flexible all-solidstate batteries of high safety and energy density. Although the conduction model was developed using the PEO:Ga-LLZO composite as a model system, this model is applicable to other composite polymer electrolytes as well, because the experimental and theoretical techniques used in this work can obviously also be applied to other superionic conductor/insulator systems.

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REFERENCES

(1) Goodenough, J. B.; Kim, Y. Challenges for Rechargeable Batteries. J. Power Sources 2011, 196, 6688−6694. (2) Xu, K. Nonaqueous Liquid Electrolytes for Lithium-Based Rechargeable Batteries. Chem. Rev. 2004, 104, 4303−4418. (3) Tarascon, J. M.; Armand, M. Issues and Challenges Facing Rechargeable Lithium Batteries. Nature 2001, 414, 359. (4) Li, Y.; Xu, B.; Xu, H.; Duan, H.; Lü, X.; Xin, S.; Zhou, W.; Xue, L.; Fu, G.; Manthiram, A.; Goodenough, J. B. Hybrid Polymer/Garnet Electrolyte with a Small Interfacial Resistance for Lithium-Ion Batteries. Angew. Chem., Int. Ed. 2017, 56, 753−756. (5) Sun, C.; Liu, J.; Gong, Y.; Wilkinson, D. P.; Zhang, J. Recent Advances in All-Solid-State Rechargeable Lithium Batteries. Nano Energy 2017, 33, 363−386. (6) Huang, B.; Xu, B.; Li, Y.; Zhou, W.; You, Y.; Zhong, S.; Wang, C.-A.; Goodenough, J. B. Li-Ion Conduction and Stability of Perovskite Li3/8Sr7/16Hf1/4Ta3/4O3. ACS Appl. Mater. Interfaces 2016, 8, 14552−14557. (7) Amores, M.; Ashton, T. E.; Baker, P. J.; Cussen, E. J.; Corr, S. A. Fast Microwave-assisted Synthesis of Li-stuffed Garnets and Insights into Li Diffusion from Muon Spin Spectroscopy. J. Mater. Chem. A 2016, 4, 1729−1736. (8) Wu, J.-F.; Chen, E.-Y.; Yu, Y.; Liu, L.; Wu, Y.; Pang, W. K.; Peterson, V. K.; Guo, X. Gallium-Doped Li7La3Zr2O12 Garnet-Type Electrolytes with High Lithium-Ion Conductivity. ACS Appl. Mater. Interfaces 2017, 9, 1542−1552. (9) Wu, J.-F.; Chen, E.-Y.; Yu, Y.; Liu, L.; Wu, Y.; Pang, W. K.; Peterson, V. K.; Guo, X. Gallium-Doped Li7La3Zr2O12 Garnet-Type Electrolytes with High Lithium-Ion Conductivity. ACS Appl. Mater. Interfaces 2017, 9, 1542−1552. (10) Catti, M.; Comotti, A.; Di Blas, S. High-Temperature Lithium Mobility in α-LiZr2(PO4)3 NASICON by Neutron Diffraction. Chem. Mater. 2003, 15, 1628−1632.

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsami.8b17279. XRD patterns, SEM and TEM images, TGA and DSC curves, ionic transference number characterization, GaLLZO/PEO interface characterization, phase-field simulation, Monte Carlo simulation and electrochemical measurements (PDF) Movie S1 (AVI) Movie S2 (AVI) 789

DOI: 10.1021/acsami.8b17279 ACS Appl. Mater. Interfaces 2019, 11, 784−791

Research Article

ACS Applied Materials & Interfaces (11) Wenzel, S.; Randau, S.; Leichtweiss, T.; Weber, D. A.; Sann, J.; Zeier, W. G.; Janek, J. Direct Observation of the Interfacial Instability of the Fast Ionic Conductor Li10GeP2S12 at the Lithium Metal Anode. Chem. Mater. 2016, 28, 2400−2407. (12) Bachman, J. C.; Muy, S.; Grimaud, A.; Chang, H.-H.; Pour, N.; Lux, S. F.; Paschos, O.; Maglia, F.; Lupart, S.; Lamp, P.; Giordano, L.; Shao-Horn, Y. Inorganic Solid-State Electrolytes for Lithium Batteries: Mechanisms and Properties Governing Ion Conduction. Chem. Rev. 2016, 116, 140−162. (13) Kato, Y.; Hori, S.; Saito, T.; Suzuki, K.; Hirayama, M.; Mitsui, A.; Yonemura, M.; Iba, H.; Kanno, R. High-Power All-Solid-State Batteries Using Sulfide Superionic Conductors. Nature Energy 2016, 1, 16030. (14) Zhao, Y.; Wu, C.; Peng, G.; Chen, X.; Yao, X.; Bai, Y.; Wu, F.; Chen, S.; Xu, X. A New Solid Polymer Electrolyte Incorporating Li10GeP2S12 into a Polyethylene Oxide Matrix for All-Solid-State Lithium Batteries. J. Power Sources 2016, 301, 47−53. (15) Goodenough, J. B.; Kim, Y. Challenges for Rechargeable Li Batteries. Chem. Mater. 2010, 22, 587−603. (16) Chan, C. K.; Yang, T.; Mark Weller, J. Nanostructured Garnettype Li7La3Zr2O12: Synthesis, Properties, and Opportunities as Electrolytes for Li-ion Batteries. Electrochim. Acta 2017, 253, 268− 280. (17) Wu, B.; Wang, S.; Evans Iv, W. J.; Deng, D. Z.; Yang, J.; Xiao, J. Interfacial Behaviours between Lithium Ion Conductors and Electrode Materials in Various Battery Systems. J. Mater. Chem. A 2016, 4, 15266−15280. (18) Zheng, J.; Tang, M.; Hu, Y.-Y. Lithium Ion Pathway within Li7La3Zr2O12-Polyethylene Oxide Composite Electrolytes. Angew. Chem., Int. Ed. 2016, 55, 12538−12542. (19) Zheng, J.; Hu, Y.-Y. New Insights into the Compositional Dependence of Li-Ion Transport in Polymer−Ceramic Composite Electrolytes. ACS Appl. Mater. Interfaces 2018, 10, 4113−4120. (20) Liu, W.; Liu, N.; Sun, J.; Hsu, P.-C.; Li, Y.; Lee, H.-W.; Cui, Y. Ionic Conductivity Enhancement of Polymer Electrolytes with Ceramic Nanowire Fillers. Nano Lett. 2015, 15, 2740−2745. (21) Zhang, J.; Zhao, J.; Yue, L.; Wang, Q.; Chai, J.; Liu, Z.; Zhou, X.; Li, H.; Guo, Y.; Cui, G.; Chen, L. Safety-Reinforced Poly(Propylene Carbonate)-Based All-Solid-State Polymer Electrolyte for Ambient-Temperature Solid Polymer Lithium Batteries. Adv. Energy Mater. 2015, 5, 1501082. (22) Chai, J.; Liu, Z.; Ma, J.; Wang, J.; Liu, X.; Liu, H.; Zhang, J.; Cui, G.; Chen, L. In Situ Generation of Poly (Vinylene Carbonate) Based Solid Electrolyte with Interfacial Stability for LiCoO2 Lithium Batteries. Adv. Sci. 2017, 4, 1600377. (23) Xin, S.; You, Y.; Wang, S.; Gao, H.-C.; Yin, Y.-X.; Guo, Y.-G. Solid-State Lithium Metal Batteries Promoted by Nanotechnology: Progress and Prospects. ACS Energy Lett. 2017, 2, 1385−1394. (24) Pan, Q.; Barbash, D.; Smith, D. M.; Qi, H.; Gleeson, S. E.; Li, C. Y. Correlating Electrode−Electrolyte Interface and Battery Performance in Hybrid Solid Polymer Electrolyte-Based Lithium Metal Batteries. Adv. Energy Mater. 2017, 7, 1701231. (25) Chen, R.; Qu, W.; Guo, X.; Li, L.; Wu, F. The Pursuit of SolidState Electrolytes for Lithium Batteries: from Comprehensive Insight to Emerging Horizons. Mater. Horiz. 2016, 3, 487−516. (26) Xi, J.; Qiu, X.; Cui, M.; Tang, X.; Zhu, W.; Chen, L. Enhanced Electrochemical Properties of PEO-Based Composite Polymer Electrolyte with Shape-Selective Molecular Sieves. J. Power Sources 2006, 156, 581−588. (27) Manuel, S. A.; Nahm, K. S. Review on Composite Polymer Electrolytes for Lithium Batteries. Polymer 2006, 47, 5952−5964. (28) Croce, F.; Appetecchi, G. B.; Persi, L.; Scrosati, B. Nanocomposite Polymer Electrolytes for Lithium Batteries. Nature 1998, 394, 456. (29) Fu, K.; Gong, Y.; Dai, J.; Gong, A.; Han, X.; Yao, Y.; Wang, C.; Wang, Y.; Chen, Y.; Yan, C.; Li, Y.; Wachsman, E. D.; Hu, L. Flexible, Solid-State, Ion-Conducting Membrane with 3D Garnet Nanofiber Networks for Lithium Batteries. Proc. Natl. Acad. Sci. U. S. A. 2016, 113, 7094.

(30) Li, D.; Chen, L.; Wang, T.; Fan, L.-Z. 3D Fiber-NetworkReinforced Bicontinuous Composite Solid Electrolyte for Dendritefree Lithium Metal Batteries. ACS Appl. Mater. Interfaces 2018, 10, 7069−7078. (31) Chen, L.; Li, Y.; Li, S.-P.; Fan, L.-Z.; Nan, C.-W.; Goodenough, J. B. PEO/Garnet Composite Electrolytes for Solid-State Lithium Batteries: from “Ceramic-in-Polymer” to “Polymer-in-Ceramic. Nano Energy 2018, 46, 176−184. (32) Zhu, P.; Yan, C.; Dirican, M.; Zhu, J.; Zang, J.; Selvan, R. K.; Chung, C.-C.; Jia, H.; Li, Y.; Kiyak, Y.; Wu, N.; Zhang, X. Li0.33La0.557TiO3 Ceramic Nanofiber-Enhanced Polyethylene OxideBased Composite Polymer Electrolytes for All-Solid-State Lithium Batteries. J. Mater. Chem. A 2018, 6, 4279−4285. (33) Liu, W.; Lee, S. W.; Lin, D.; Shi, F.; Wang, S.; Sendek, A. D.; Cui, Y. Enhancing Ionic Conductivity in Composite Polymer Electrolytes with Well-Aligned Ceramic Nanowires. Nat. Energy 2017, 2, 17035. (34) Zhai, H.; Xu, P.; Ning, M.; Cheng, Q.; Mandal, J.; Yang, Y. A Flexible Solid Composite Electrolyte with Vertically Aligned and Connected Ion-Conducting Nanoparticles for Lithium Batteries. Nano Lett. 2017, 17, 3182−3187. (35) Bae, J.; Li, Y.; Zhang, J.; Zhou, X.; Zhao, F.; Shi, Y.; Goodenough, J. B.; Yu, G. A 3D Nanostructured HydrogelFramework-Derived High-Performance Composite Polymer Lithium-Ion Electrolyte. Angew. Chem., Int. Ed. 2018, 57, 2096−2100. (36) Yang, T.; Zheng, J.; Cheng, Q.; Hu, Y. Y.; Chan, C. K. Composite Polymer Electrolytes with Li7La3Zr2O12 Garnet-Type Nanowires as Ceramic Fillers: Mechanism of Conductivity Enhancement and Role of Doping and Morphology. ACS Appl. Mater. Interfaces 2017, 9, 21773−21780. (37) Zhang, X.; Liu, T.; Zhang, S.; Huang, X.; Xu, B.; Lin, Y.; Xu, B.; Li, L.; Nan, C.-W.; Shen, Y. Synergistic Coupling between Li6.75La3Zr1.75Ta0.25O12 and Poly(vinylidene fluoride) Induces High Ionic Conductivity, Mechanical Strength, and Thermal Stability of Solid Composite Electrolytes. J. Am. Chem. Soc. 2017, 139, 13779− 13785. (38) Armand, M. Polymer solid electrolytes - an overview. Solid State Ionics 1983, 9−10, 745−754. (39) Zhang, J.; Zhao, N.; Zhang, M.; Li, Y.; Chu, P. K.; Guo, X.; Di, Z.; Wang, X.; Li, H. Flexible and Ion-Conducting Membrane Electrolytes for Solid-State Lithium Batteries. Nano Energy 2016, 28, 447−454. (40) Yu, S.; Schmidt, R. D.; Garcia-Mendez, R.; Herbert, E.; Dudney, N. J.; Wolfenstine, J. B.; Sakamoto, J.; Siegel, D. J. Elastic Properties of the Solid Electrolyte Li7La3Zr2O12 (LLZO). Chem. Mater. 2016, 28, 197−206. (41) Kokal, I.; Somer, M.; Notten, P. H. L.; Hintzen, H. T. Sol−Gel Synthesis and Lithium Ion Conductivity of Li7La3Zr2O12 with GarnetRelated Type Structure. Solid State Ionics 2011, 185, 42−46. (42) Evans, J.; Vincent, C. A.; Bruce, P. G. Electrochemical Measurement of Transference Numbers in Polymer Electrolytes. Polymer 1987, 28, 2324−2328. (43) Liang, C. C. Conduction Characteristics of the Lithium IodideAluminum Oxide Solid Electrolytes. J. Electrochem. Soc. 1973, 120, 1289−1292. (44) Yamada, H.; Bhattacharyya, A. J.; Maier, J. Extremely High Silver Ionic Conductivity in Composites of Silver Halide (AgBr, AgI) and Mesoporous Alumina. Adv. Funct. Mater. 2006, 16, 525−530. (45) Dudney, N. J. Enhanced Ionic Conduction in AgCl-Al2O3 Composites Induced by Plastic Deformation. J. Am. Ceram. Soc. 1987, 70, 65−68. (46) Liang, J.; Li, L.; Tong, K.; Ren, Z.; Hu, W.; Niu, X.; Chen, Y.; Pei, Q. Silver Nanowire Percolation Network Soldered with Graphene Oxide at Room Temperature and Its Application for Fully Stretchable Polymer Light-Emitting Diodes. ACS Nano 2014, 8, 1590−1600. (47) Jiang, S.; Wagner, J. B. A Theoretical Model for Composite ElectrolytesI. Space Charge Layer as a Cause for Charge-Carrier Enhancement. J. Phys. Chem. Solids 1995, 56, 1101−1111. 790

DOI: 10.1021/acsami.8b17279 ACS Appl. Mater. Interfaces 2019, 11, 784−791

Research Article

ACS Applied Materials & Interfaces (48) Shahi, K.; Wagner, J. B. Enhanced Ionic Conduction in Dispersed Solid Electrolyte Systems (DSES) and/or Multiphase Systems: Agl-Al2O3, Agl-SiO2, Agl-Fly Ash, and Agl-AgBr. J. Solid State Chem. 1982, 42, 107−119. (49) Dieterich, W. Transport in Random Composite Materials Philosophical. Philos. Mag. B 1989, 59, 97−104. (50) Lauer, U.; Maier. Electrochemical Analysis of Anomalous Conductivity Effects in the AgCl-AgI Two Phase System. J. Phys. Chem. 1992, 96, 111−119. (51) Sata, N.; Eberman, K.; Eberl, K.; Maier, J. Mesoscopic Fast Ion Conduction in Nanometre-Scale Planar Heterostructures. Nature 2000, 408, 946−949. (52) Bunde, A.; Dieterich, W.; Roman, E. Dispersed Ionic Conductors and Percolation Theory. Phys. Rev. Lett. 1985, 55, 5−8. (53) Roman, H. E.; Bunde, A.; Dieterich, W. Conductivity of Dispersed Ionic Conductors: A Percolation Model with Two Critical Points. Phys. Rev. B: Condens. Matter Mater. Phys. 1986, 34, 3439− 3445. (54) Maier, J. Defect Chemistry and Conductivity Effects in Heterogeneous Solid Electrolytes. J. Electrochem. Soc. 1987, 134, 1524. (55) Maier, J. Nanoionics: Ion Transport and Electrochemical Storage in Confined Systems. Nat. Mater. 2005, 4, 805−815. (56) Chen, C.-C.; Fu, L.; Maier, J. Synergistic, Ultrafast Mass Dtorage and Removal in Artificial Mixed Conductors. Nature 2016, 536, 159−164. (57) Mebane, D. S.; De Souza, R. A. A Generalised Space-Charge Theory for Extended Defects in Oxygen-Ion Conducting Electrolytes: from Dilute to Concentrated Solid Solutions. Energy Environ. Sci. 2015, 8, 2935−2940. (58) Tong, X.; Mebane, D. S. Kinetic Modeling of Near-Interface Defect Segregation During Thermal Annealing of Oxygen-Conducting Solid Electrolytes. Solid State Ionics 2017, 299, 78−81. (59) Mebane, D. S. A. Variational Approach to Surface Cation Segregation in Mixed Conducting Perovskites. Comput. Mater. Sci. 2015, 103, 231−236. (60) Zhu, J.; Wang, J.; Mebane, D. S.; Nonnenmann, S. S. In Situ Surface Potential Evolution along Au/Gd:CeO2 Electrode Interfaces. APL Mater. 2017, 5, 042503. (61) Denesyuk, N. A.; Hansen, J. P. Wetting Ttransitions of Ionic Solutions. J. Chem. Phys. 2004, 121, 3613−3624. (62) Bunde, A.; Dieterich, W.; Roman, H. E. Monte Carlo Studies of Ionic Conductors Containing an Insulating Second Phase. Solid State Ionics 1986, 18−19, 147−150.

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DOI: 10.1021/acsami.8b17279 ACS Appl. Mater. Interfaces 2019, 11, 784−791