A new class of sulfide electrolytes, (1-x)LiCl-xLiBr-2Li(3)PS(4)(x = 0, 0.25, 0.50, 0.75, and 1.0), was synthesized, and characterized their stable temperature range, ionic-conductivity and applicability for all-solid-state lithium metal battery. The optimal heat-treatment temperature of the synthesis process is relatively low, i.e., 200?. Ionic conductivity of the electrolyte increases with increasing LiBr ratio, and maximum ionic conductivity at 25 ? is 1.7 mScm(-1) with x = 0.75. At higher heat-treatment temperature, above 250 ?, a low-ionic-conduction crystalline phase appears in the electrolyte, and at that time, ionic conductivity decreases to a similar value to that of the amorphous precursor used in the synthesis process. Since the electrolyte does not contain a transition metal, it is applicable to the lithium-metal secondary system. A reversible lithium deposition-stripping reaction was demonstrated by cyclic voltammogram, the results of which indicate that the electrolyte is applicable to a typical 4-V rechargeable lithium-metal secondary system. The Coulombic efficiency of the first charge-discharge cycle is approximately 75%, and reversible capacity of 185 mAhg(-1) was verified by a Li/0.25LiCl-0.75LiBr2Li3PS4/NCA pelletized-cell test. It is concluded from these results that the proposed low-temperature synthesized sulfide electrolytes will reduce energy consumption for material production, and such a low carbon-footprint process meets the demand of the future sustainable society.

Transition metal sulfides have shown to improve the performance of lithium-sulfur batteries both with liquid and solid electrolytes. In this work, the beneficial effect of copper sulfide for enabling high areal capacity lithium-sulfur all-solid-state batteries is shown. Copper sulfide-carbon (CuSC) and three different copper sulfide-sulfur-carbon (CuSS) composites are investigated as positive electrodes in all-solid-state lithium-sulfur batteries. The composites are prepared via facile and low-cost mechanochemical ball-milling. It is found that the CuS/C ratio greatly influences the redox properties of the CuSC cathode. Scanning electron microscopy, ex-situ X-ray diffraction, and galvanostatic cycling were also conducted to evaluate the CuSS composite electrodes in Li vertical bar LiI-Li3PS4 vertical bar CuS-S-C solid-state cells. High mass loading cells made using these composite electrodes deliver capacities as high as 1600 mAh g((CuS+S))(-1) and 7 mAh cm(-2) at 20 degrees C. The higher density of CuS also leads to larger volumetric capacities, up to 3900 mAh cm((CuS+S))(-3), thus enabling a potential energy density gain up to 15% with respect to a conventional Carbon-Sulfur cathode.

The current state of the art insertion cathode materials provides energy density around 700 Wh kg-1. In order to improve the energy density of batteries, conversion type materials are considered. Among these, Sulfur is regarded as promising cathode material as it theoretically provides a high specific capacity of 1672 mAh g-1 and energy density of 2500 Wh kg-1, a value three times higher than the conventional state of the art cathode materials.[1] Unfortunately, the Sulfur conversion reaction is accompanied by 80% volume change and polysulfide shuttling[2]. The use of composite cathodes, incorporating carbonaceous materials and metal sulfides, can help improve cell performance by buffering volume changes while creating effective electron conduction pathways and enhancing sulfur utilization by catalytic effects[3]. Recently we studied the effect of different metal sulfides on the sulfur cathode and realized their beneficial effect towards improved electrochemical performance. This work shows how the synergy between CuS (a transition metal sulfide) and S can lead to extraordinary high areal capacities, improved cycling life, higher energy efficiency, and volumetric energy density compared to a pure S cathode. The all-solid-state cell using an inorganic solid-state Li2S-P2S5-LiI electrolyte, metal sulfides-containing composite cathodes, and Li metal showed stable cycling (1200 cycles over one year) with high specific capacity up to (970 mAh g-1). High mass loading (5 mg cm-2 of active material equivalent to 22 mg cm-2 of total cathode mass) cells using composite (CuS-Sulfur) electrodes deliver capacities as high as 1600 mAh g-1 (CuS+S) and 7 mAh cm-2 at 20 °C. The higher density of CuS also leads to larger volumetric capacities, up to 3900 mAh cm-3(CuS+S), thus enabling an energy density gain up to 15% with respect to a conventional Carbon-Sulfur cathode. Different technics such as ex-situ XRD, SEM, EIS and Galvanostatic cycling elucidate the metal sulfide conversion mechanism. Figure 1

As the theoretical limit of intercalation material-based lithium-ion batteries is approached, alternative chemistries based on conversion reactions are presently considered. The conversion of sulfur is particularly appealing as it is associated with a theoretical gravimetric energy density up to 2510 Wh kg(-1). In this paper, three different carbon-iron disulfide-sulfur (C-FeS2-S) composites are proposed as alternative positive electrode materials for all-solid-state lithium-sulfur batteries. These are synthesized through a facile, low-cost, single-step ball-milling procedure. It is found that the crystalline structure (evaluated by X-ray diffraction) and the morphology of the composites (evaluated by scanning electron microscopy) are greatly influenced by the FeS2:S ratio. Li/LiI-Li3PS4/C-FeS2-S solid-state cells are tested under galvanostatic conditions, while differential capacity plots are used to discuss the peculiar electrochemical features of these novel materials. These cells deliver capacities as high as 1200 mAh g((FeS2+S))(-1) at the intermediate loading of 1 mg cm(-2) (1.2 mAh cm(-2)), and up to 3.55 mAh cm(-2) for active material loadings as high as 5 mg cm(-2) at 20 degrees C. Such an excellent performance, rarely reported for (sulfur/metal sulfide)-based, all solid-state cells, makes these composites highly promising for real application where high positive electrode loadings are required.

Quinoid compounds are important candidates of organic active materials for lithium-ion batteries. However, its high solubility to organic electrolyte solutions and low redox potential are known as their major drawbacks. To circumvent these issues, we have designed and synthesized a tandem-tetracyanoquinonedimethane type cathode-active material, 11,11,12,12,13,13,14,14-octacyano-1,4,5,8-anthradiquinotetramethane (OCNAQ), that has four redox sites per molecule, high redox potential and suppressed solubility to electrolyte solution. Synthesized OCNAQ has been found to have two-step redox reactions by cyclic voltammetry, and each step consists of two-electron reactions. During charge-discharge tests using selected organic cathode-active materials with a lithium metal anode, the cell voltages obtained from OCNAQ are higher than those for 11,11-dicyanoanthraquinone methide (AQM) as expected, due to the strong electron-withdrawing effect of the cyano groups. Unfortunately, even with the use of the organic active material, the issue of dissolution to the electrolyte solution cannot be suppressed completely; however, appropriate choice of the electrolyte solutions, glyme-based electrolyte solutions in this study, give considerable improvement of the cycle retention (98% and 56% at 10 and 100 cycles at 0.5C, respectively). The specific capacity and energy density obtained in this study are 206 mAh g(-1) and 554 mWh g(-1) with respect to the cathode active material.

There have been several reports on improvements of the performance of all solid-state battery using lithium metal oxide coatings on the cathode active material. However, the mechanism of the performance improvement remains unclear. To better understand the effect of the surface coating, we studied the impact of diamond-like carbon (DLC) coating on LiNi0.8Co0.15Al0.05O2 (NCA) by chemical vapor deposition (CVD). The DLC coated NCA showed good cycle ability and rate performance. This result is further supported by reduction of the interfacial resistance of the cathode and electrolyte observed in impedance spectroscopy. The DLC layer was analyzed by transmission electron microscopy electron energy loss spectroscopy (TEM-EELS). After 100 cycles the sample was analyzed by X-ray photo spectroscopy (XPS), and Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS). These analyses showed that the thickness of the coating layer was around 4 nm on average, acting to hinder the side reactions between the cathode particle and the solid electrolyte. The results of this study will provide useful insights for understanding the nature of the buffer layer for the cathode materials. (C) 2016 Elsevier B.V. All rights reserved.

Sulfide based solid electrolytes are of considerable practical interest for all solid-state batteries due to their high ionic conductivity and softness at room temperature. In particular, iodine containing lithium thiophosphate is known to exhibit high ionic conductivity but its applicability in solid-state battery remains to be examined. To demonstrate the possibility of the iodine doped solid electrolyte (SE), LiI-Li3PS4 was used to construct two different types of test cells were prepared, Li/SE/S and Li/SE/LiNi0.80Co0.15Al0.05 cells. The solid electrolyte, LiI-Li3PS4 showed a high ionic conductivity approximately 1.2 mScm-1 at 25 ℃. Within 100 cycles, the capacity retention was better in Li/SE/S cell, and the red-ox shuttle was not observed due to physical blockage of SE layer. The capacity fade was approximately 4% from the maximum capacity observed at 10th cycle, after 100 cycles in Li/SE/S cell. On the contrary, the capacity fade was much larger in Li/SE/LiNi0.80Co0.15Al0.05 cell, probably due to the decomposition of the electrolyte at the operating potential range. Nevertheless, both the Li/SE/LiNi0.80Co0.15Al0.05 and Li/SE/S cells exhibited the high coulombic efficiencies above 99.6% and 99.9% during charge-discharge cycle test, respectively. This fact indicates that a high energy density can be possible without an excess lithium metal anode. In addition, it was particularly interesting that the SE showed a reversible capacity about 260 mAhg-1-SE. This electrolyte may have not only as a role of the ion conduction, but also as a catholite.

The investigation of a lithium-carbon composite (Li–C) anode for application in all-solid-state battery, based on (Li2S)0.75-(P2S5)0.25 glassy thio-LISICON electrolyte (Li2S-P2S5) is herein reported. The Li–C anode material is prepared by a mechanochemical, single step synthesis procedure. The Li–C/electrolyte interface is characterized in terms of cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic cycling in comparison with lithium metal, in order to evaluate the improvements in terms of resistance and lithium stripping deposition ability. Li–C anode powder is pressed into a pellet together with the Li2S-P2S5 electrolyte and Li2ZrO3-coated, Li[Ni0.8Co0.15Al0.05]O2 cathode powder (NCA-LZO), to form a new type of solid-state battery operating at room temperature. The Li–C/Li2S-P2S5/NCA-LZO battery shows remarkable cycling performance under galvanostatic conditions, particularly if compared to a more conventional configuration employing lithium metal as the anode. In addition, the all solid-state battery is characterized at various current densities, showing satisfactory rate capability. Under long term-cycling condition, performed at low current and prolonged to more than 250days, the cell shows a stability over 100cycles without fading. This is considered a remarkable result suggesting the solid-state cell here studied as suitable candidate for efficient and safe energy storage.

In recent years, the lithium-sulfur (Li-S) secondary battery has been energetically researched worldwide as a good candidate for next-generation secondary batteries. The sulfur active material has a theoretical capacity of 1675 mAh g -1 and is abundant and highly inexpensive. However, several issues are associated with the use of Li-S secondary batteries, such as low utilization due to the insulating property of sulfur and the redox shuttle phenomenon caused by the dissolution of polysulfides generated during the discharge process. In the present work, we have developed a Li-S secondary battery using the carbon nanotube (CNT) technoloy. Multiwalled-CNTs were directly grown on a nickel current collector by using the thermal chemical vapor deposition (CVD) method. The CNT films were used as the electrode for the Li-S battery. The S-CNT cathode was fabricated by impregnating it with molten sulfur. Then, sulfur powder was uniformly placed on the CNT film and heated at more than the melting point of 113°C. Our CNT has a diameter of 10-15 nm and a length of 200-600 µm. Therefore, the CNT electrode has a wide reaction area owing to its large specific surface area. In addition, the active materials can react rapidly because the electrons quickly access through the CNTs that connect directly with the current collector. At IMLB 2014, we reported that coin-cell-type Li-S batteries with a sulfur loading of up to 10 mg cm -2 operate at a current density of 0.5 mA cm -2 [1]. However, more sulfur loading is required, in order to achieve the electrode capacity of 300 Wh kg -1 for practical usage. As sulfur loading increased to more than 10 mg cm -2 , the discharge capacity decreased dramatically, probably owing to be attributed to inhomogeneous sulfur distribution in the CNT film. Moreover, the CNT films fell off the nickel current collector because of the shrinkage of the CNT bundles owing to the absorption of sulfur. Therefore, we attempted to synthesize harder CNT films with homogeneously impregnated sulfur. A thick amorphous carbon layer was coated on the CNTs by optimizing the thermal CVD process, thus making the CNT films harder. Moreover, the adhesiveness between the CNTs and the nickel current collector was enhanced, which improved CNT exfoliation. For homogeneous distribution, sulfur impregnation was performed in vacuum. The sulfur was considered to spread over the CNT films more uniformly. We could obtain the stable coin-cell-battery performance with sulfur loading of up to 20 mg cm -2 , and the capacity was estimated to be more than 300 Wh kg -1 [2]. We manufactured 1 Ah-class pouch cell, with electrode surface area of 50 cm 2 . Reference [1] N.Tsukahara, presented at The 17 th International Meeting on Lithium Batteries, Como, 2014 (unpublished) [2] T. Yamada, presented at The 56 th Battery Symposium, Nagoya, 2015 (unpublished) Figure 1

This study describes the characteristics of a lithium-ion battery employing an ionic liquid (IL)-based electrolyte, a Li2O-ZrO2-coated Li[Ni0.8Co0.15Al0.05O2] cathode, and a nanostructured tin-carbon (Sn-C) composite anode. The structure and morphology of the cathode and anode materials were studied using X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The properties of the IL-based electrolyte were studied in terms of conductivity, lithium-ion transport, electrochemical and thermal stability by electrochemical impedance spectroscopy, voltammetry, and thermogravimetry. The battery, based on a lithium intercalation/de-intercalation process at the cathode and a lithium alloying/de-alloying process at the anode, showed a stable capacity of 100mAhg(-1) evolving at approximately 3.3V. The cell configuration proposed here is expected to have high safety due to the nonflammability of the IL-based electrolyte.

The surface of LiNi0.8Co0.15Al0.05O2 (NCA) cathode material was coated with diamond like carbon (DLC) by chemical vapor deposition method, in order to prevent the side reaction at the interface for sulfide based all-solid state lithium-ion batteries. The DLC coated material showed a higher capacity with good cyclability and high rate performance. The interface resistance between the cathode active material and the solid electrolyte significantly decreases by DLC coating onto the NCA powder. The discharge capacity of DLC coated sample at 0.05C was 113 mAhg−1 while that of bared one was about 102 mAhg−1. The charge and discharge cut off potentials were 4.0 and 2.8 V, respectively. The thickness of the DLC coated layer was verified by transmission electron microscope (TEM), and was about 3`5 nm. The sp2 bonding ratio of the DLC coated LiNi0.8Co0.15Al0.05O2 powder was estimated from the C-KELNES spectra to be 50`55%. DLC coating could avoid formation of an inactive layer when surface impurities of NCA react with the sulfide electrolyte to form at irreversible passivation byproduct. This layer of impurities obstructs the Li-ion transport at the interface, and therefore increases the interfacial resistance and decreases the rate capability for bare samples. In this work, the diamond like carbon (DLC) coating were proposed for the first time as buffer coating layers for all-solid state battery. We demonstrated that the buffer layer is not needed to have a lithium conductivity to reduce the interface resistance between cathode material and sulfide based electrolyte.

A crystalline solid electrolyte, Li7P3S11, was synthesized by a liquid-phase reaction of Li2S and P2S5 in an organic solvent. A precursor, which was a mixture of solvated Li3PS4 and Li4P2S7, was prepared by mixing Li2S and P2S5 powders in 1,2-dimethoxyethane (DME) solvent. After a vacuum drying of the precursor, the crystalline phase of Li7P3S11 was obtained by heat treatment at 250 degrees C for I h in Ar atmosphere. The Li7P3S11 sample showed high ionic conductivity of 2.7 x 10(-4) S cm(-1) at room temperature. The liquid-phase synthesis of the solid electrolyte has advantages for mass-production of all-solid-state batteries. (C) 2014 Elsevier B.V. All rights reserved.

LiAlO2-coated LiNi1/3Mn1/3Co1/3O2 powders were prepared by a sol–gel method associated with ultra-sonication, and the obtained LiAlO2-coated LiNi1/3Mn1/3Co1/3O2 was investigated as positive electrode materials for all-solid-state batteries with sulfide-based solid electrolytes. All-solid-state lithium batteries were assembled with the obtained LiAlO2-coated LiNi1/3Mn1/3Co1/3O2 powders and with amorphous Li3PS4 as solid electrolytes. The charge–discharge cycle performance of the all-solid-state cells was improved by the LiAlO2-coating on LiNi1/3Mn1/3Co1/3O2 powders. The LiAlO2 coating was effective in suppressing an increasing of the interfacial resistance between the LiNi1/3Mn1/3Co1/3O2 electrode material and the sulfide based solid electrolyte, Li3PS4, during charge–discharge cycling. The battery with the 1.0mol% LiAlO2-coated LiNi1/3Mn1/3Co1/3O2 showed an initial discharge capacity of 134 mAhg−1 and the battery retained the capacity more than 124 mAhg−1 even after 400 charge–discharge cycles at a current density of 11 mAg−1 at room temperature.

In this work we characterize a solid-state lithium–sulfur battery using a Li2S–P2S5 glass-type electrolyte. The electrolyte is prepared by powder pellet-pressing and the effect of the applied pressure on the ionic conductivity as well as its temperature dependence is studied by electrochemical impedance spectroscopy. The lithium–sulfur battery electrochemical process is studied by potentiodynamic cycling with galvanostatic acceleration (PCGA) at an operating temperature of 80°C. The cycling behavior of the battery is studied by repeated charge/discharge in galvanostatic conditions. The results demonstrate that the electrolyte has a conductivity ranging from 1*10−4 to 5*10−3 S cm−1 by increasing the temperature from 0°C to 80°C, respectively. Furthermore, the PCGA measurement shows a maximum capacity referred versus sulfur mass of the order of 1200 mAh g−1, while the cycling test, performed at C/20, indicates a steady-state capacity of the order of 400 mAh g−1, a working voltage of 2.1V and a resulting theoretical energy density of 840Whkg−1. Considering the results we believe that the solid-state, lithium sulfur cell with the Li2S–P2S5 electrolyte may be proposed as high-energy density battery for safe, low-cost energy storage applications.

An all-solid-state lithium-ion battery (ASSB) using non-flammable solid electrolytes is a candidate for a next-generation battery. Although the excellent cycle performance and its high energy density are suggested in the literature, a practical size battery has not been appeared yet. In this paper, we have adopted a sulfide based electrolyte, Li2S-P2S5 (80:20 mol%) to a rocking chair type lithium ion battery. The electrochemical cell consists of a Li2O-ZrO2 coated LiNi0.8Co0.15Al0.05O2 (NCA) cathode, an artificial graphite anode and the sulfide based electrolyte without any organic and inorganic liquids. The cathode charge transfer resistance is significantly reduced by the Li2O-ZrO2 coating. The total cell resistance of the Li2O-ZrO2 (LZO) coated NCA adopted cell is approximately one quarter of non-treated one. A standard type single cell with the nominal capacity of 100 mAh at 25 degrees C is fabricated by wet printing process, and its capacity retention is approximately 80% at 100 cycles. Also, a I Ah class battery was constructed by stacking the single cells, and demonstrated. (C) 2013 Elsevier B.V. All rights reserved.

In this study, the authors developed the all-solid-state Li-ion cells by using the quasi-solid-state electrolyte consists of a pseudo-ternary mixture of room temperature ionic liquid (RTIL) - Li-salt - fumed silica nanoparticles. The all-solid-state cells with LiCoO2, LiMnO2, LiNiO2 and Li4Ti5O12 as cathodes and Li-metal as an anode were assembled and the battery performances were evaluated. Although comparatively thicker composite cathodes such as approximately 50 mu m were employed, the all-solid-state cells successfully achieved high cathode utilizations of LiCoO2, LiMnO2, LiNiO2 and Li4Ti5O12 such as 80 %, 70 %, 75 % and 60 %, respectively, at 308 K with 0.05 C. The slow transport of Li-ions in our all-solid-state cells essentially limited the battery performances as in the cells with RTIL - Li-salt as electrolytes.