Chemically Evolved Composite Lithium-Ion Conductors with Lithium

Jul 11, 2017 - Automotive Research and Development Division, Hyundai Motor Company, Uiwang-si, Gyeonggi-do, Republic of Korea. ¶ Advanced Analysis Ce...
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Chemically Evolved Composite Lithium-Ion Conductors with Lithium Thiophosphates and Nickel Sulfides Mansoo Park,†,# Hun-Gi Jung,‡,# Wo Dum Jung,† Soo Young Cho,† Bin-Na Yun,‡ Yoon Sung Lee,‡ Sungjun Choi,† Junsung Ahn,† Jaemin Lim,§ Ju Young Sung,§ Yong-Jun Jang,§ Jae-Pyoung Ahn,¶ Jong-Ho Lee,† and Hyoungchul Kim*,† †

High-Temperature Energy Materials Research Center, Korea Institute of Science and Technology, Seoul, Republic of Korea Center for Energy Convergence Research, Korea Institute of Science and Technology, Seoul, Republic of Korea § Automotive Research and Development Division, Hyundai Motor Company, Uiwang-si, Gyeonggi-do, Republic of Korea ¶ Advanced Analysis Center, Korea Institute of Science and Technology, Seoul, Republic of Korea ‡

S Supporting Information *

ABSTRACT: The development and application of all-solid-state batteries with a fast lithium-ionic conductor are hampered by structural instability and rigid stoichiometry restrictions. Here, we present a family of lithium thiophosphate prototypes with a novel principle, controlling sulfur deficiencies with the addition of nickel sulfide-based additives, for fast lithium-ion conduction and distinct electrochemical stability under the extended material constituent. Well-controlled sulfur deficiency of the Li3PS4 framework accompanied by nickel sulfide additive offers the notable increase of lithium-ion conductivity (2 × 10−3 S cm−1 at 25 °C) and high electrochemical stability (up to 10 V vs Li/Li+) in a wide composition range. We further confirm the potential application of our fast composite lithium-ion conductor as an electrolyte for the all-solid-state battery with 117 mAh g−1 capacity delivery and stable cycle life.

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limitations, such as structural instability and strict stoichiometry requirements.30,31 In contrast, Li3PS4, one of the most stable LPS compounds, is not considered to be a promising candidate as a solid electrolyte owing to its low lithium-ion conductivity [under 5 × 10−4 (for the glass-ceramic material) and 3 × 10−7 S cm−1 (for the γ-phase) at 25 °C],1,32,33 in spite of its superior thermodynamic and electrochemical stability. These features result from the tetrahedral PS43− units and the infinite [010] lithium-ion pathways from tetrahedral to octahedral sites. Interestingly, recent studies11,34 shed light on how to improve the lithium-ion conduction of Li3PS4. Improvements can be made by (i) controlling the high-temperature (metastable) βphase for fast ion conduction, (ii) promoting the surface conduction pathway with a nanoporous structure, (iii) cation substitution, and (iv) alkali halide interactions. These efforts

he performance of most solid-state superionic conductors, including those used in batteries, fuel cells, and sensors, is based on the structural instability and rigid stoichiometry restrictions. Thus, the development of electrochemically stable and compositionally flexible superionic conductors has been a great challenge, and they have not been demonstrated yet in the field of all-solid-state batteries in particular. Over the past two decades, the lithium thiophosphate (LPS) family, having a variety of crystalline states (crystalline,1−13 glass-ceramic,14−24 amorphous25−29), has been extensively studied. Some LPS compounds [thio-LISION II/III analogues (e.g., Li 3.25 Ge 0 .25 P 0. 75 S 4 , 2 Li 1 0 GeP 2 S 12 , 5 , 1 0 Li 10 SnP 2 S 12 , 7 Li 3.45 Si 0.45 P 0.55 S 4 , 8 Li 3.833 Sn 0.833 As 0.166 S 4 , 9 Li9.6P3S12,12 and Li9.54Si1.74P1.44S11.7Cl0.312), Li7P3S11 family,3,15−24 and argyrodite-type phases (e.g., Li 6PS5Cl,4,6 Li6PS5Br4)] exhibit high lithium-ion conductivity (σion) of the order of 1 × 10−3 S cm−1 and have been acknowledged to be a promising family of solid electrolytes for next-generation allsolid-state lithium-ion batteries. Similar to the above-mentioned limitations of superionic conductors, these well-known LPS solid electrolytes also suffer from inherent ionic conductor © XXXX American Chemical Society

Received: June 8, 2017 Accepted: July 5, 2017

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ACS Energy Letters

Figure 1. (a) Variations in lithium-ion conductivity of the LPN(9:3:z) with different amounts (z) of the Ni3S2 at 25 °C. (b) Arrhenius plots of lithium-ion conductivities for LPN(9:3:1). Two typical LPS solid electrolytes, Li3PS4 and Li7P3S11, are also shown.

have increased lithium-ion conductivity to 6.4 × 10−4 S cm−1 at 25 °C, without compromising structural stability and material compatibility. However, because of the inherent one-dimensional ion transport mechanism in β-Li3PS4, this material has, to date, eluded further conductivity enhancement. In addition, substituting cation and nanostructuring high-temperature βphase causes issues related to material instability and poor processability, which are not suitable for a solid electrolyte. Tuning the lithium-ion transport physics of Li3PS4 materials (for high lithium-ion conductivity of over 1.0 × 10−3 S cm−1), while simultaneously achieving electrochemical stability (for long-term, high C-rates) has not been accomplished. Here, we report a fast composite lithium-ion conductor that demonstrates high structural stability over a flexible range of constituents, achieved by controlling the sulfur deficiency in the thiophosphate framework. Such a fast lithium-ion conducting structure is obtained by employing sulfur transition phenomena through the addition of nickel sulfide into the thiophosphate matrix. The crystal structure and properties of this material have been verified through X-ray diffraction (XRD) and transmission electron microscopy (TEM) investigations. The potential of this material as a solid electrolyte for all-solid-state batteries is discussed based on its electrochemical charge− discharge operation at room temperature. We synthesized the fast composite lithium-ion conductor using Li2S, P2S5, and Ni3S2 as starting materials. Li3PS4, from Li2S and P2S5, serves as the framework for the matrix, and Ni3S2 is included as a minor component in order to tune the matrix system. These materials were homogeneously mixed and mechanically alloyed with a planetary mill and ZrO2 milling media for 8 h at 650 rpm. The resulting amorphous powder was crystallized in high-temperature annealing at 260 °C for 2 h. Further experimental details are provided in the Supporting Information. Hence, the addition of Ni3S2 into the Li3PS4 matrix [i.e., (Li2S)9(P2S5)3] provides a material with the starting materials’ empirical formula (Li2S)x(P2S5)y(Ni3S2)z [hereafter, denoted as LPN(x:y:z)]. Figure 1a presents the change in lithium-ion conductivity of LPN at room temperature with fixed x and y compositions (x = 9 and y = 3 for Li3PS4 matrix), as a function of the input molar amounts (z) of Ni3S2 additive, i.e., LPN (9:3:z). Interestingly, the measured ionic conductivity of the LPN system is larger than that of an equivalent LPS (LPN without Ni3S2), (Li2S)9(P2S5)3 = 6(Li3PS4), for both asmilled and as-annealed, samples. The lithium-ion conductivities of LPN(9:3:z) show an initial sharp rise with increasing Ni3S2

amounts, which plateaus in the high Ni3S2 composition range. At 25 °C, the highest conductivity achieved for LPN(9:3:z) is 2.0 × 10−3 S cm−1 and corresponded to a Ni3S2 composition of z = 1. To verify the absence of electronic conduction in various LPN samples, we examined the electronic conductivity σel (and the ion transference number tion) by direct-current polarization measurements, which provided a negligible value of σel = 3.2 × 10−9 S cm−1 (and tion = 0.99999) for LPN(9:3:1) (see Figure S1 in the Supporting Information). From the data provided in Figures 1a and S1, we conclude that the LPN(9:3:z) system is a pure lithium-ion conductor when z lies in the range 0 ≤ z < 4; consequently, these materials are applicable as solid electrolytes for all-solid-state batteries. It is significant to adjust the appropriate amount of Ni3S2 to suppress the electronic conductivity because NiS has electronic conduction and it forms an electron-conducting connected phase when z ≥ 4. The temperature-dependent lithium-ion conductivity of LPN(9:3:1) shows typical Arrhenius behavior in the temperature range of 25−150 °C (Figure 1b). Generally, the LPN(9:3:1) structure possesses higher lithium-ion conductivity over all practical temperatures (25−150 °C) as compared with two typical LPS compounds, Li3PS4 and Li7P3S11. The activation energy (Ea) for lithium-ion conduction is predicted using the Arrhenius equation, that is

σion =

σ◦ ⎛ Ea ⎞ exp⎜ − ⎟ T ⎝ kBT ⎠

(1)

where σo is the pre-exponential factor, T temperature, and kB the Boltzmann constant. Application of eq 1 to LPN(9:3:1) reveals that this material has a significantly suppressed activation energy (0.297 eV) compared to that of Li3PS4 (0.402 eV), and the value is close to that of Li7P3S11 (0.227 eV), a LPS superionic conductor. These results indicate that LPN(9:3:1) operates through a different lithium-ion conduction mechanism compared to Li3PS4 that is associated with the interaction of the Li3PS4 matrix with the Ni3S2 additive, although the dominant matrix composition of LPN(9:3:1) is still maintained as that of Li3PS4. In addition to the observation of fast lithium-ion conduction in LPN(9:3:1), the LPN family is found to possess two distinct features, electrochemical stability and a wide compositional range tolerance. Using the Li/LPN(9:3:1)/stainless-steel asymmetric cell, we first investigated the electrochemical stability of LPN(9:3:1) using cyclic voltammetry at a scan 1741

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Figure 2. (a) Cyclic voltammogram of the LPN(9:3:1). (b) Contour map showing the relationship between lithium-ion conductivity and the normalized ternary composition parameters of the LPN family with measured samples indicated. Typical LPS compounds (c = 0), Li3PS4 and Li7P3S11, are also included.

Figure 3. (a) XRD patterns of as-milled and annealed LPN(9:3:1), with reference XRD patterns of Li3PS4, Ni3S2, and NiS. (b) TEM image of LPN(9:3:1) after annealing, with SAD patterns of the matrix and the NiS nanoparticle. The numbered points in the TEM image correspond to the SAD pattern positions. (c) Comparison of the SAD patterns of Li3PS4−δ, δ=1/6 and LPN(9:3:1).

rate of 1 mV s−1, the results of which are shown in Figure 2a. No additional reaction or decomposition peaks are observed in the −0.5 to 10.0 V potential range, with the exception of that for typical cathodic lithium deposition (Li+ + e− → Li) and anodic lithium stripping (Li → Li+ + e−). This means that the LPN(9:3:1) material is electrochemically stable (up to 10.0 V vs Li+/Li) and has excellent material compatibility with the lithium electrode. To explore compositional flexibility, the relationship between lithium-ion conductivity and the ternary composition parameters of the LPN family was next examined. Note that the normalized molar ratios [a, b, and c, where a = x/ (x + y + z), b = y/(x + y + z), and c = z/(x + y + z)] were used as composition parameters in the ternary contour map. We explored a total of 49 LPN family members (including 4 LPS compounds) in order to produce the contour map displayed in Figure 2b. This conductivity contour map predicts two prominent maxima (i.e., for a = 0.692, b = 0.231, and c = 0.077, σion,LPN(9:3:1) = 2.0 × 10−3 S cm−1; for a = 0.700, b = 0.180, and c = 0.120, σion,LPN(7:1.8:1.2) = 1.8 × 10−3 S cm−1) and a wide compositional range (0.65 < a for Li2S < 0.75, 0.15 < b for P2S5 < 0.25, and 0.05 < c for Ni3S2 < 0.18) with fast lithium-ion conduction (i.e., σion > 1.0 × 10−3 S cm−1). On the basis of the fact that most LPS solid electrolytes that exhibit high lithiumion conductivities (over 1 × 10−3 S cm−1) have highly rigid stoichiometry restrictions, we confirm that the LPN system provides the potential for significant extensions in composi-

tional flexibility without any deterioration in high ionic conductivity. The XRD patterns of LPN(9:3:1) before and after annealing are displayed in Figure 3a. On the basis of the broad diffraction peaks, Li3PS4 appears to be amorphic. The diffraction peaks for Li3PS4 after annealing become narrow, illustrating that the amorphous phase of Li3PS4 crystallizes during thermal exposure. It is interesting to note that NiS nanoparticles are also observed after the annealing process. The compositional evolution of XRD crystallographic data for LPN(9:3:z) (0 ≤ z ≤ 5) after annelaing are also provided in Figure S2. These results also show that Li3PS4 and NiS coexist at z < 4, while the NiS structure dominates at z ≥ 4. The associated structural evolution and controlling evidence are discussed in detail, with the following TEM results. The TEM micrograph of LPN(9:3:1), after annealing at 260 °C, is shown in Figure 3b (left) and demonstrates that the microstructure of this material is mostly crystalline. For your reference, low-magnification TEM and energy-dispersive X-ray spectroscope images of the annealed LPN(9:3:1) sample showing uniformly embedded NiS nanoparticles in Li3PS4 matrix are also provided (Figure S3). The amorphous Li3PS4 of the matrix, observed before annealing, has evolved into crystalline structures during thermal exposure. This conclusion is based on the diffraction pattern in the right-top panel (point-1) of Figure 3b, which displays sharp and complete rings that are closely matched to the index of Li3PS4. What is noteworthy in these electron diffraction 1742

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Figure 4. (a) Charge−discharge voltage profiles of the all-solid-state cells with the LPN family at 25 °C. (b) Discharge voltage profiles at difference C-rates. (c) Cycling performance of the all-solid-state NCM/LPN/In cell.

volume36−38 and partially distorted sulfur sublattice (from hcp to bcc),39 which suggests the approach of using the sulfur deficiency helps overcome the inherent one-dimensional pathway in Li3PS4. These proof-of-concept experiments explicitly reveal that sulfur deficiency in the LPN(9:3:1) medium leads to high lithium-ion conductivity. Hence, we postulate that lithium-ion conductivity can be controlled by adjusting the stoichiometry of sulfur in LPS compounds. To investigate the electrochemical performance of all-solidstate batteries using the developed composite LPN lithium-ion conductors, cells with cathode composites and electrolytes composed of various combinations of the conductors developed in this study were fabricated and compared for battery performance. In these cells, lithium nickel cobalt manganese oxide (LiNi0.6Co0.2Mn0.2O2, NCM) and metallic indium foil were used as the cathode and anode, respectively. The electrochemical performance during charge and discharge at room temperature of the cells using the LPN(9:3:1) conductor are depicted in Figure 4. For the systematic assessment of compatibility toward cells containing lithiumion conductors of two compositions above σion = 1 × 10−3 S cm−1, i.e., LPN(8:2:1) and LPN(9:3:1), two cells using two cathode composites were fabricated: LPN(8:2:1)-NCM/ LPN(9:3:1)/In and LPN(9:3:1)-NCM/LPN(9:3:1)/In. Charge and discharge tests were performed in the 2.0−3.6 V potential window (versus Li−In) at each C-rate, which were calculated based on 180 mAh g−1 = 1 C-rate. The n C-rate means the current density to charge or discharge fully in 1/n hour. At the first cycle, with a low applied current density (0.02 C-rate) (Figure 4a), the cells exhibit discharge capacities of about 116 and 117 mAh g−1 for NCM cathode composites, using the LPN(9:3:1) and LPN(8:2:1) conductors, respectively. In addition, the data in Figure 4b,c, under conditions of increased C-rates and extended cycle life, clearly show that our LPN conductors are promising candidates for applications in

patterns is that most of the embedded Ni3S2 particles have chemically turned into NiS (point-2, right-middle panel of Figure 3b). According to the equilibrium phase diagram of Ni and S,35 in which NiS lies close to Ni3S2, the Ni3S2 of the feedstock powder is thermodynamically capable of attaining more sulfur atoms by adjusting its stoichiometry in a sulfur-rich environment. Therefore, as the Ni3S2 is converted into NiS during thermal exposure, it leaves behind a sulfur-deficient Li3PS4‑δ matrix. In addition, such embedded NiS particles act as a glass modifier and alter the network structure of PSx. As a consequence, we infer that the increase in lithium-ion conductivity observed for LPN(9:3:1), after annealing, is attributed to the development of a NiS embedded sulfurdeficient Li3PS4−δ matrix, promoting the number of nonbridging sulfur and edge sharing polyhedral connection (P2S62−), which increases the free volume in the structure. To further substantiate this mechanism, LPN was subjected to a proof-of-concept demonstration. We intentionally prepared a sulfur-deficient sample, Li3PS4−δ, δ=1/6, by adjusting the amount of phosphorus and sulfur pure-elements added (without applying the Ni3S2 additive). Figure 3c shows the electron diffraction pattern of Li3PS4−δ, δ=1/6 after annealing, presented next to that of LPN(9:3:1) for comparative purposes. The sulfur-deficient Li3PS4−δ (δ = 1/6) exhibits a diffraction pattern identical to that of LPN(9:3:1), which indicates that these two materials exist in the same phase. The related additional results are summarized in Figure S4. The lithium-ion conductivity behavior of these proof-of-concept samples as a function of sulfur deficiency interestingly was found to correspond exactly to what was observed for LPN (Figure 1a). For your reference, the Raman spectra of sulfur-deficient Li3PS4−δ (δ = 1/6) are shown in Figure S5: a peak attributed to P2S62− ion-cluster gradually increases as sulfur deficiency increases. We think that the mixed anion effect offers more than one-dimensional lithium-conducting pathways by introducing more free 1743

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practical all-solid-state batteries. However, the low initial efficiency, of about 65%, should be solved through our further studies by controlling side reactions at the electrode/electrolyte interface. Moreover, from the cell performance data in Figure 4, we are aware that the selection of the appropriate composition for inclusion in the cathode composite is also key to realizing long life and high-power all-solid-state batteries. In conclusion, we have explored a composite lithium-ion conductor of LPN that was synthesized by a milling process to achieve an amorphous state, followed by annealing at 260 °C. The LPN(9:3:1) material shows high lithium-ion conductivity that exceeds 2.0 × 10−3 S cm−1 at room temperature. All of the Ni3S2 additive was found to chemically evolve into NiS during the annealing process. We attribute the high lithium-ion conduction to sulfur deficiencies that establish more transport pathways for the lithium ions. For proof-of-concept studies, a sulfur-deficient Li3PS4−δ sample, prepared without the addition of Ni3S2, exhibited a lithium-ion conductivity that is very close to that of LPN. The chemically evolved LPN system with the embedded NiS particle and sulfur-deficient LPS matrix has three major advantages over existing LPS materials: (i) An inclusion like Ni3S2 facilitates easy and economical control of sulfur-deficiency in the production of sulfur-deficient LPS matrix of interest. (ii) Various pristine LPS compounds that exhibit high lithium-ion conductivities (over 1 × 10−3 S cm−1) have highly rigid stoichiometry restrictions; however, the LPN family tolerates a flexible range of constituents, which broadens its processing window and, in turn, its potential applications. (iii) LPN, when integrated as a solid electrolyte in an all-solidstate battery, was demonstrated to maintain high structural stability during manufacturing processes and electrochemical charge−discharge operations. This battery delivered a capacity of 117 mAh g−1 and was cycled without severe decay for over 100 cycles. It is our hope that methods to control sulfur nonstoichiometry and its composite prototype, LPN lithiumion conductors, will provide a general new approach to increasing lithium-ion conduction in solid-state batteries, in turn opening up opportunities for the further development of high energy density batteries with high structural stability.

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The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work was funded by grants from Hyundai NGV and Hyundai Motor Company, Award No. 2I22810. This work was also supported in part by the Energy Efficiency & Resources Core Technology Program of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) granted financial resource from the Ministry of Trade, Industry & Energy, Republic of Korea (No. 20152020106100). H.-G.J. was partly supported by the National Research Council of Science and Technology (CAP-14-2-KITECH). We are grateful to Yanghee Kim and Min Kyung Cho for valuable comments and discussion on the focused ion beam sampling and TEM analysis.

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EXPERIMENTAL METHODS Detailed experimental methods are provided in the Supporting Information. ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsenergylett.7b00497. Further experimental details, additional conductivity data, XRD patterns, and TEM results for LPN family and various proof-of-concept Li3PS4−δ samples (PDF)

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REFERENCES

(1) Tachez, M.; Malugani, J. P.; Mercier, R.; Robert, G. IonicConductivity of and Phase-Transition in Lithium Thiophosphate Li3PS4. Solid State Ionics 1984, 14, 181−185. (2) Kanno, R.; Murayama, M. Lithium Ionic Conductor ThioLISICON. J. Electrochem. Soc. 2001, 148, A742−A746. (3) Yamane, H.; Shibata, M.; Shimane, Y.; Junke, T.; Seino, Y.; Adams, S.; Minami, K.; Hayashi, A.; Tatsumisago, M. Crystal Structure of a Superionic Conductor. Solid State Ionics 2007, 178, 1163−1167. (4) Rao, R. P.; Adams, S. Studies of Lithium Argyrodite Solid Electrolytes for All-solid-state Batteries. Phys. Status Solidi A 2011, 208, 1804−1807. (5) Kamaya, N.; Homma, K.; Yamakawa, Y.; Hirayama, M.; Kanno, R.; Yonemura, M.; Kamiyama, T.; Kato, Y.; Hama, S.; Kawamoto, K.; et al. A Lithium Superionic Conductor. Nat. Mater. 2011, 10, 682− 686. (6) Boulineau, S.; Courty, M.; Tarascon, J.-M.; Viallet, V. Mechanochemical Synthesis of Li-Argyrodite Li6PS5X (X = Cl, Br, I) as Sulfur-Based Solid Electrolytes for All Solid State Batteries Application. Solid State Ionics 2012, 221, 1−5. (7) Bron, P.; Johansson, S.; Zick, K.; Schmedt auf der Gunne, J.; Dehnen, S.; Roling, B. Li10SnP2S12: An Affordable Lithium Superionic Conductor. J. Am. Chem. Soc. 2013, 135, 15694−15697. (8) Hori, S.; Suzuki, K.; Hirayama, M.; Kato, Y.; Saito, T.; Yonemura, M.; Kanno, R. Synthesis, Structure, and Ionic Conductivity of Solid Solution, Li10+δM1+δP2‑δS12 (M = Si, Sn). Faraday Discuss. 2014, 176, 83−94. (9) Sahu, G.; Lin, Z.; Li, J. C.; Liu, Z. C.; Dudney, N.; Liang, C. D. Air-Stable, High-Conduction Solid Electrolytes of Arsenic-Substituted Li4SnS4. Energy Environ. Sci. 2014, 7, 1053−1058. (10) Hori, S.; Taminato, S.; Suzuki, K.; Hirayama, M.; Kato, Y.; Kanno, R. Structure-Property Relationships in Lithium Superionic Conductors Having a Li10GeP2S12-Type Structure. Acta Crystallogr., Sect. B: Struct. Sci., Cryst. Eng. Mater. 2015, 71, 727−736. (11) Rangasamy, E.; Liu, Z. C.; Gobet, M.; Pilar, K.; Sahu, G.; Zhou, W.; Wu, H.; Greenbaum, S.; Liang, C. D. An Iodide-Based Li7P2S8I Superionic Conductor. J. Am. Chem. Soc. 2015, 137, 1384−1387. (12) 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. Nat. Energy 2016, 1, 16030. (13) Sedlmaier, S. J.; Indris, S.; Dietrich, C.; Yavuz, M.; Dräger, C.; von Seggern, F.; Sommer, H.; Janek, J. Li4PS4I: A Li+ Superionic Conductor Synthesized by a Solvent-Based Soft Chemistry Approach. Chem. Mater. 2017, 29, 1830−1835. (14) Hayashi, A.; Hama, S.; Minami, T.; Tatsumisago, M. Formation of Superionic Crystals from Mechanically Milled Li2S-P2S5 Glasses. Electrochem. Commun. 2003, 5, 111−114.

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. ORCID

Hun-Gi Jung: 0000-0002-2162-2680 Hyoungchul Kim: 0000-0003-3109-660X Author Contributions #

M.P. and H.-G.J. contributed equally to this work. 1744

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ACS Energy Letters

(37) Minami, K.; Hayashi, A.; Ujiie, S.; Tatsumisago, M. Structure and Properties of Li2S-P2S5-P2S3 Glass and Glass-Ceramic Electrolytes. J. Power Sources 2009, 189, 651−654. (38) Minami, K.; Hayashi, A.; Ujiie, S.; Tatsumisago, M. Electrical and Electrochemical Properties of Glass-Ceramic Electrolytes in the Systems Li2S-P2S5-P2S3 and Li2S-P2S5-P2O5. Solid State Ionics 2011, 192, 122−125. (39) Wang, Y.; Richards, W. D.; Ong, S. P.; Miara, L. J.; Kim, J. C.; Mo, Y.; Ceder, G. Design Principles for Solid-State Lithium Superionic Conductors. Nat. Mater. 2015, 14, 1026−1032.

(15) Mizuno, F.; Hayashi, A.; Tadanaga, K.; Tatsumisago, M. New, Highly Ion-Conductive Crystals Precipitated from Li2S-P2S5 Glasses. Adv. Mater. 2005, 17, 918−921. (16) Mizuno, F.; Hayashi, A.; Tadanaga, K.; Tatsumisago, M. New Lithium-Ion Conducting Crystal Obtained by Crystallization of the Li2S-P2S5 Glasses. Electrochem. Solid-State Lett. 2005, 8, A603−A606. (17) Mizuno, F.; Hayashi, A.; Tadanaga, K.; Tatsumisago, M. High Lithium Ion Conducting Glass-Ceramics in the System Li2S-P2S5. Solid State Ionics 2006, 177, 2721−2725. (18) Hayashi, A.; Minami, K.; Mizuno, F.; Tatsumisago, M. Formation of Li+ Superionic Crystals from the Li2S-P2S5 MeltQuenched Glasses. J. Mater. Sci. 2008, 43, 1885−1889. (19) Hayashi, A.; Minami, K.; Ujiie, S.; Tatsumisago, M. Preparation and Ionic Conductivity of Li7P3S11‑z Glass-Ceramic Electrolytes. J. Non-Cryst. Solids 2010, 356, 2670−2673. (20) Teragawa, S.; Aso, K.; Tadanaga, K.; Hayashi, A.; Tatsumisago, M. Formation of Li2S-P2S5 Solid Electrolyte from N-Methylformamide Solution. Chem. Lett. 2013, 42, 1435−1437. (21) Ohtomo, T.; Hayashi, A.; Tatsumisago, M.; Tsuchida, Y.; Hama, S.; Kawamoto, K. All-Solid-State Lithium Secondary Batteries Using the 75Li2S·25P2S5 Glass and the 70Li2S·30P2S5 Glass-Ceramic as Solid Electrolytes. J. Power Sources 2013, 233, 231−235. (22) Seino, Y.; Ota, T.; Takada, K.; Hayashi, A.; Tatsumisago, M. A Sulphide Lithium Super Ion Conductor is Superior to Liquid Ion Conductors for Use in Rechargeable Batteries. Energy Environ. Sci. 2014, 7, 627−631. (23) Xu, R. C.; Xia, X. H.; Wang, X. L.; Xia, Y.; Tu, J. P. Tailored Li2S−P2S5 Glass-Ceramic Electrolyte by MoS2 Doping, Possessing High Ionic Conductivity for All-solid-state Lithium-sulfur Batteries. J. Mater. Chem. A 2017, 5, 2829−2834. (24) Xu, R. C.; Xia, X. H.; Li, S. H.; Zhang, S. Z.; Wang, X. L.; Tu, J. P. All-solid-state lithium-sulfur Batteries based on a Newly Designed Li7P2.9Mn0.1S10.7I0.3 Superionic Conductor. J. Mater. Chem. A 2017, 5, 6310−6317. (25) Mercier, R.; Malugani, J.-P.; Fahys, B.; Robert, G. Superionic Conduction in Li2S-P2S5-LiI-Glasses. Solid State Ionics 1981, 5, 663− 666. (26) Lühder, K.; Schmidt, L.; Schnittke, A.; Füllbier, H. A Study on Novel Lithium-Iodine and Lithium-Bromine Solid Electrolyte Batteries. J. Power Sources 1992, 40, 257−263. (27) Sakamoto, R.; Tatsumisago, M.; Minami, T. Preparation of Fast Lithium Ion Conducting Glasses in the System Li2S-SiS2-Li3N. J. Phys. Chem. B 1999, 103, 4029−4031. (28) Hayashi, A.; Hama, S.; Morimoto, H.; Tatsumisago, M.; Minami, T. Preparation of Li2S-P2S5 Amorphous Solid Electrolytes by Mechanical Milling. J. Am. Ceram. Soc. 2001, 84, 477−479. (29) Aso, K.; Sakuda, A.; Hayashi, A.; Tatsumisago, M. All-SolidState Lithium Secondary Batteries Using NiS-Carbon Fiber Composite Electrodes Coated with Li2S−P2S5 Solid Electrolytes by Pulsed Laser Deposition. ACS Appl. Mater. Interfaces 2013, 5, 686−690. (30) Takada, K. Progress and Prospective of Solid-State Lithium Batteries. Acta Mater. 2013, 61, 759−770. (31) Goodenough, J. B.; Kim, Y. Challenges for Rechargeable Li Batteries. Chem. Mater. 2010, 22, 587−603. (32) Tatsumisago, M. Encyclopedia of Electrochemical Power Sources; Elesevier B.V.: Amsterdam, The Netherlands, 2009. (33) Homma, K.; Yonemura, M.; Kobayashi, T.; Nagao, M.; Hirayama, M.; Kanno, R. Crystal Structure and Phase Transitions of the Lithium Ionic Conductor Li3PS4. Solid State Ionics 2011, 182, 53− 58. (34) Liu, Z.; Fu, W.; Payzant, E. A.; Yu, X.; Wu, Z.; Dudney, N. J.; Kiggans, J.; Hong, K.; Rondinone, A. J.; Liang, C. Anomalous High Ionic Conductivity of Nanoporous β-Li3PS4. J. Am. Chem. Soc. 2013, 135, 975−978. (35) Okamoto, H. Ni-S (Nickel-Sulfur). J. Phase Equilib. Diffus. 2009, 30, 123. (36) Ahn, B. T.; Huggins, R. A. Phase Behavior and Conductivity of Li2SiS3 Composition. Solid State Ionics 1991, 46, 237−242. 1745

DOI: 10.1021/acsenergylett.7b00497 ACS Energy Lett. 2017, 2, 1740−1745