Preparation and characterization of B2S3-based chalcogenide glasses

The discovery of the fast ion conducting B[subscript]2S[subscript]3-based glasses has been one of the most significant development in the field of solid electrolytes. Considerable experimental studies have been done to maximize conductivities and chemical stabilities of these glass systems. Recently, the study of the structure and properties of these glasses compared to their oxide analog has become important;The IR spectra of M[subscript]2S + B[subscript]2S[subscript]3 (M = Li, K, Rb and Cs) and MS + B[subscript]2S[subscript]3 (M = Sr and Ba) thioborate glasses have shown the monotonic increase in tetrahedral boron units at the expense of thioboroxyl six-membered ring groups in a manner similar to that found in the alkali borate glasses in the low alkali glasses. Although the Li and K thioborate glasses were found to have structural similarities in the high alkali glasses, the Rb, Cs, Sr and Ba thioborate glasses have significant differences which arises from the fact that the alkali and alkaline earth ion plays a dominant role in controlling local structural environments;The density data and IR spectra for these glasses have shown the monotonic increase in tetrahedral boron units in the low alkali region, whereas the destruction of tetrahedral boron units arising from the formation of trigonal boron units with terminal non-bridging sulfurs for the high alkali glasses. In contrast to this behavior, the Tg measurements have shown the decreasing Tg with the addition of alkali modifier in the alkali thioborate glasses in the low alkali region. It is apparent that, although the SRO are similar in both systems, there are significant differences in the IRO and we have proposed that sulfur ions plays a dominant role in degrading IRO structure rather than enhancing

Improvements to the Overpotential of All-Solid-State Lithium-Ion Batteries during the Past Ten Years

After the research that shows that Li10GeP2S12 (LGPS)-type sulfide solid electrolytes can reach the high ionic conductivity at the room temperature, sulfide solid electrolytes have been intensively developed with regard to ionic conductivity and mechanical properties. As a result, an increasing volume of research has been conducted to employ all-solid-state lithium batteries in electric automobiles within the next five years. To achieve this goal, it is important to review the research over the past decade, and understand the requirements for future research necessary to realize the practical applications of all-solid-state lithium batteries. To date, research on all-solid-state lithium batteries has focused on achieving overpotential properties similar to those of conventional liquid-lithium-ion batteries by increasing the ionic conductivity of the solid electrolytes. However, the increase in the ionic conductivity should be accompanied by improvements of the electronic conductivity within the electrode to enable practical applications. This essay provides a critical overview of the recent progress and future research directions of the all-solid-state lithium batteries for practical applications

Stacked porous tin phosphate nanodisk anodes

Stacked porous octahedral tin phosphate Sn(2)P(2)O(7) nanodisks, with a thickness and a width of 20 nm and 200 nm, respectively, were prepared from quenching hydrothermally prepared (SnHPO(4))(2)center dot H(2)O at 600 degrees C. The first discharge capacity was 600 mA h g(-1) while the capacity retention, even after 220 cycles, was 93%.close7

High-Performance Heterostructured Cathodes for Lithium-Ion Batteries with a Ni-Rich Layered Oxide Core and a Li-Rich Layered Oxide Shell

The Ni-rich layered oxides with a Ni content of >0.5 are drawing much attention recently to increase the energy density of lithium-ion batteries. However, the Ni-rich layered oxides suffer from aggressive reaction of the cathode surface with the organic electrolyte at the higher operating voltages, resulting in consequent impedance rise and capacity fade. To overcome this difficulty, we present here a heterostructure composed of a Ni-rich LiNi0.7Co0.15Mn0.15O2 core and a Li-rich Li1.2-xNi0.2Mn0.6O2 shell, incorporating the advantageous features of the structural stability of the core and chemical stability of the shell. With a unique chemical treatment for the activation of the Li2MnO3 phase of the shell, a high capacity is realized with the Li-rich shell material. Aberration-corrected scanning transmission electron microscopy (STEM) provides direct evidence for the formation of surface Li-rich shell layer. As a result, the heterostructure exhibits a high capacity retention of 98% and a discharge- voltage retention of 97% during 100 cycles with a discharge capacity of 190 mA h g(-1) (at 2.0-4.5 V under C/3 rate, 1C = 200 mA g(-1)).ope

Efficient CO2 Utilization via a Hybrid Na-CO2 System Based on CO2 Dissolution

Carbon capture, utilization, and sequestration technologies have been extensively studied to utilize carbon dioxide (CO2), a greenhouse gas, as a resource. So far, however, effective technologies have not been proposed owing to the low efficiency conversion rate and high energy requirements. Here, we present a hybrid Na-CO2 cell that can continuously produce electrical energy and hydrogen through efficient CO2 conversion with stable operation for over 1,000 hr from spontaneous CO2 dissolution in aqueous solution. In addition, this system has the advantage of not regenerating CO2 during charging process, unlike aprotic metal-CO2 cells. This system could serve as a novel CO2 utilization technology and high-value-added electrical energy and hydrogen production device

High-Performance Direct Methanol Fuel Cells with Precious-Metal-Free Cathode

Direct methanol fuel cells (DMFCs) hold great promise for applications ranging from portable power for electronics to transportation. However, apart from the high costs, current Pt-based cathodes in DMFCs suffer significantly from performance loss due to severe methanol crossover from anode to cathode. The migrated methanol in cathodes tends to contaminate Pt active sites through yielding a mixed potential region resulting from oxygen reduction reaction and methanol oxidation reaction. Therefore, highly methanol-tolerant cathodes must be developed before DMFC technologies become viable. The newly developed reduced graphene oxide (rGO)-based Fe-N-C cathode exhibits high methanol tolerance and exceeds the performance of current Pt cathodes, as evidenced by both rotating disk electrode and DMFC tests. While the morphology of 2D rGO is largely preserved, the resulting Fe-N-rGO catalyst provides a more unique porous structure. DMFC tests with various methanol concentrations are systematically studied using the best performing Fe-N-rGO catalyst. At feed concentrations greater than 2.0 m, the obtained DMFC performance from the Fe-N-rGO cathode is found to start exceeding that of a Pt/C cathode. This work will open a new avenue to use nonprecious metal cathode for advanced DMFC technologies with increased performance and at significantly reduced cost.open0

High-Performance Direct Methanol Fuel Cells with Precious-Metal-Free Cathode

Direct methanol fuel cells (DMFCs) hold great promise for applications ranging from portable power for electronics to transportation. However, apart from the high costs, current Pt-based cathodes in DMFCs suffer significantly from performance loss due to severe methanol crossover from anode to cathode. The migrated methanol in cathodes tends to contaminate Pt active sites through yielding a mixed potential region resulting from oxygen reduction reaction and methanol oxidation reaction. Therefore, highly methanol-tolerant cathodes must be developed before DMFC technologies become viable. The newly developed reduced graphene oxide (rGO)-based Fe-N-C cathode exhibits high methanol tolerance and exceeds the performance of current Pt cathodes, as evidenced by both rotating disk electrode and DMFC tests. While the morphology of 2D rGO is largely preserved, the resulting Fe-N-rGO catalyst provides a more unique porous structure. DMFC tests with various methanol concentrations are systematically studied using the best performing Fe-N-rGO catalyst. At feed concentrations greater than 2.0 m, the obtained DMFC performance from the Fe-N-rGO cathode is found to start exceeding that of a Pt/C cathode. This work will open a new avenue to use nonprecious metal cathode for advanced DMFC technologies with increased performance and at significantly reduced cost.open0

Scalable approach to multi-dimensional bulk Si anodes via metal-assisted chemical etching

Specific design and optimization of the configuration of micro-scale materials can effectively enhance battery performance, including volumetric density. Herein, we employed commercially available low-cost bulk silicon powder to produce multi-dimensional silicon composed of porous nanowires and micro-sized cores, which can be used as anode materials in lithium-ion batteries, by combining a metal deposition and metal-assisted chemical etching process. Nanoporous silicon nanowires of 5-8 mu m in length and with a pore size of similar to 10 nm are formed in the bulk silicon particle. The silicon electrodes having multi-dimensional structures accommodate large volume changes of silicon during lithium insertion and extraction. These materials show a high reversible charge capacity of similar to 2400 mAh g(-1) with an initial coulombic efficiency of 91% and stable cycle performance. The synthetic route described herein is simple, low-cost, and mass producible (high yield of 40-50% in tens of gram scale), and thus, provides an effective method for producing high-performance anode materials.close373

Mass production of uniform-sized nanoporous silicon nanowire anodes via block copolymer lithography

We present a simple, mass production of nonporous and nanoporous silicon nanowire anodes by combining block copolymer masks and metal catalytic etching. Carbon coated nanoporous silicon nanowire anodes exhibit a highly stable cycling performance with a reversible charge capacity of 1500 mA h g(-1).close231