Sulfones are polar molecules that can be used as thermally stable electrolyte solvents for Li-ion batteries (LIBs). Li salts form stoichiometric solvates with sulfones in the electrolytes. The melting points of the solvates tend to be higher than room temperature, thereby limiting the operating temperature range of the batteries. In this study, the applicability of ternary eutectic mixtures of LiN­(SO2F)2 (LiFSA), sulfolane (SL), and dimethyl sulfone (DMS) as LIB electrolytes was assessed. Relative to the binary LiFSA–sulfone electrolytes, the ternary eutectic electrolytes remained liquid over a wide temperature range due to the increased entropy of mixing. Sulfone-bridged Li+–sulfone–Li+ and anion-bridged Li+–FSA––Li+ network structures were formed in the eutectic electrolyte with a composition of [LiFSA]/[SL]/[DMS] = 1/1.5/1.5. Pulsed-field gradient NMR measurements revealed that the Li+ ion dynamically exchanges sulfones and anions and diffuses more rapidly than these ligands, resulting in the relatively high Li+ transference number of the electrolyte. Highly reversible charge–discharge processes of the LiCoO2 and graphite electrodes were attained using the ternary eutectic electrolyte. The rate capability of the Li/LiCoO2 cell in the eutectic electrolyte was comparable to that of the cell in the conventional 1 M LiPF6 in an ethylene carbonate/dimethyl carbonate solution despite its lower ionic conductivity.

Li-ion-hopping conduction is known to occur in certain highly concentrated electrolytes, and this conduction mode is effective for achieving lithium batteries with high rate capabilities. Herein, we investigated the effects of the solvent structure on the hopping conduction of Li ions in highly concentrated LiBF 4 /sulfone electrolytes. Raman spectroscopy revealed that a Li + ion forms complexes with sulfone and anions, and contact ion pairs and ionic aggregates are formed in the highly concentrated electrolytes. Li + exchanges ligands (sulfone and BF 4 − ) rapidly to produce unusual hopping conduction in highly concentrated electrolytes. The structure of the solvent significantly influences the hopping conduction process. We measured the selfdiffusion coefficients of Li + (D Li ), anions (D anion ), and sulfone solvents (D sol ) in electrolytes. The ratio of the self-diffusion coefficients (D Li /D sol ) tended to be higher for cyclic sulfones (sulfolane and 3-methylsulfolane) than for acyclic sulfones, which suggests that cyclic sulfone molecules facilitate Li-ion hopping. The hopping conduction increases the Li + -transference number (t Li abc + ) under anion-blocking conditions, and t Li abc + of [LiBF 4 ]/[cyclic sulfone] = 1/2 is as high as 0.8.

Cu2SnS3 (CTS) p-type semiconductors are expected to be applied as a light absorption material for low-cost thin-film solar cells due to their advantageous physical properties. The influence of sodium addition to CTS thin films was investigated by comparing Na-free CTS and Na-doped CTS fabricated on alkali-free glass substrates. Grain growth for Na-free CTS, which has a Cu/Sn composition ratio of approximately 2.0, did not occur below 570 °C. In contrast, the addition of sodium to the CTS increased the grain sizes with an increase in the annealing temperature. Even with Na-free and Na-doped CTS, the grain sizes increased with a decrease in the Cu/Sn composition ratio. These results show that an excess of Sn combined with the presence of sodium accelerate the grain growth of CTS. Photovoltaic cells using the Na-doped CTS with a Cu/Sn ratio of 1.81 exhibited an open-circuit voltage of 242 mV, a short-circuit current density of 26.5 mA/cm2, a fill factor of 0.523, and a conversion efficiency of 3.35%. The cells using CTS without sodium did not exhibit good photovoltaic characteristics due to the small grain sizes.

Highly concentrated Li salt/aprotic solvent solutions are promising electrolytes for next-generation batteries. Understanding the Li + ion transport process is crucial for designing novel battery electrolytes.In this study, we systematically investigated the phase behavior, solvate structures, and Li + transport properties of binary mixtures comprising lithium bis(trifluoromethanesulfonyl)amide (LiTFSA) and various sulfones, such as sulfolane (SL), 3-methyl sulfolane (MSL), dimethyl sulfone (DMS), ethyl methyl sulfone (EMS), and ethyl isopropyl sulfone (EiPS). Except for the MSL system, the [LiTFSA]/[sulfone] = 1/2 mixtures remained in a liquid state at room temperature, thus enabling a systematic comparison of the Li + transport properties in the highly concentrated electrolytes. In highly concentrated liquid electrolytes, Li + ions diffuse by exchanging ligands (sulfone and TFSA). Li + ions diffuse faster than TFSA in all electrolytes except the EiPS-based electrolyte at a composition of [LiTFSA]/[sulfone] = 1/2, resulting in high Li + transference numbers. SL-based electrolytes show higher ionic conductivity and Li + transference numbers than other sulfone-based electrolytes. Consequently, sulfone solvents with compact molecular sizes and low energy barriers of conformational change are favorable for enhancing the Li + ion transport in the electrolytes.

The binary compound SnS consists of elements that are non‐toxic, inexpensive, and abundant in the Earth's crust. It is a p‐type semiconductor with a band gap energy of 1.3 eV and an absorption coefficient of 104 cm−1, and is therefore a potential candidate for use as a solar cell absorber material. In this study, SLG/Mo/SnS/CdS/ZnO:Al/Al and SLG/Mo/SnS/ZnO/ZnO:Al/Al SnS thin‐film solar cells with different buffer layers were fabricated using a co‐evaporation method. The dependence of the photovoltaic properties of the SnS thin‐film solar cells with CdS or ZnO as the buffer layer was investigated. We demonstrate that the device with a ZnO buffer layer exhibited higher conversion efficiency and short‐circuit current density compared to the device with a CdS buffer layer.