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A self-learning artificial intelligence system for an autonomous molecular search was recently utilized in place of laborious material development processes by humans. In this approach, because the evaluation of unsuitable or unrealistic candidates considerably decreases the search efficiency, prior knowledge of the chemistry and engineering requirements should be embedded into the molecular-generative algorithm. However, when using naive rule-based restrictions, one must implement the complex rule logic into the code each time, depending on the materials and potential applications. Herein, we propose a molecular-generative method using a maze game to control the allowable constituent fragments of molecules, which improves the flexibility and consistency to implement the rules. We performed an autonomous search for optimized cation structures of high Li-ion conductive ionic liquids evaluated by molecular dynamics simulations, in its practically reasonable scope defined by the maze game. From the search, we discover that acyl ammonium cations are favorable for high Li-ion conductivity because of the high association between the cations and Li ions. These results broaden our existing insight owing to the ability to explore beyond our practical experiences.

A new battery catholyte material composed of equimolar 4-methoxy-2,2,6,6-tetramethylpiperidine 1-oxyl (MT) and lithium bis(trifluoromethanesulfonyl) imide (LT) and its highly concentrated mixtures with water were studied using experiments and molecular dynamics simulations. It was found that the dynamic properties of the mixture are significantly improved by adding even a small amount of water. Detailed analysis on the solvation structure in the mixtures reveals that water molecules can break the strong interaction between MT and LT, and thus the ions can move more freely. As a result, the ionic conductivity of the catholyte mixtures increases with increasing water molar ratio in the water concentration range covered in the current work. The performance of the catholyte mixture systems was also tested in battery cells. The best utility efficiency of the capacity was found for the mixture of water:MT:LT ratio at 5.3:1:1. Water molar ratios of 5 to 6 were also found to be the lowest concentration at which MT and LT are fully saturated by water. These results provide insightful understanding of the performance of these battery catholytes.

Owing to their extremely high theoretical energy density, non-aqueous Li-air batteries have received remarkable attention in recent years. Ionic Liquids (ILs), molten salts that are liquid at room temperature, have been investigated as potential electrolytes in Li-air batteries due to their negligible vapor pressure, good thermal stability, and wide electrochemical windows. However, compared to conventional organic electrolytes, ILs generally have higher viscosity and, consequently, lower ionic conductivity and ion diffusivity. Therefore, we have selected eight low-viscosity ILs containing the bis(trifluoromethanesulfonyl)imide ([TFSI]-) anion, and their physical properties were characterized. The diffusivities of the cation and anion of the ILs were measured with pulsed-field-gradient spin-echo (PFG-SE) NMR Spectroscopy. In addition, the I-V performances of three characteristic ILs were tested in a Li-O2 battery. The solubility of O2 in the ILs and IL-Li[TFSI] mixtures, an additional property that can affect Li-air battery performance, was also measured using a gravimetric microbalance.

It is widely acknowledged that Li2CO3and LiOH as side-products in the operation of a Li–air cell should be completely removed in the cycling to avoid cumulative negative effect on the cycling performance. However, the understanding of their electrochemical decomposition is limited. We report a mechanistic analysis of the intrinsic barrier to electrochemically decompose Li2CO3and LiOH. Our first-principles study reveals that the decomposition is rate-limited by the electrochemical extraction of Li+, whereas the chemical release of anions is barrierless once the applied voltage overcomes the energy penalty to generate a Li-deficient surface. The voltage necessary for the decomposition of Li2CO3is predicted to be in the range of 4.38–4.61 V, whereas for LiOH it is in the range of 4.67–5.02 V. The maximum charge efficiency to decompose Li2CO3and LiOH in the operation of a Li–air cell is estimated to be 66% and 61%, respectively. The high intrinsic barrier originates from the energy cost of oxidizing redox-inert anions for the charge neutrality when lithium is extracted. Therefore, one strategy for lowering the barrier is incorporating redox-active species as a charge mediator to compensate the electron loss during the decomposition.

The influence of single-walled carbon nanotube (SWCNT) architectures for facilitating charge transport in mesoscopic semiconductor films has been probed using a TiO2/Ru(II) trisbipyridyl complex system. Both transient absorption and emission measurements indicate that the SWCNT network in the film has no noticeable influence on the charge injection process from the excited Ru(II) trisbipyridyl complex into TiO2particles. However, it plays an important role in improving the charge separation, as the rate of back electron transfer between the oxidized sensitizer (Ru(III)) and the injected electrons becomes slower in the presence of the SWCNT scaffold. The beneficial aspect of charge collection by SWCNT has been further explored by carrying out photoelectrochemical measurements. The dye-sensitized solar cells constructed using this SWCNT scaffold show an improvement in the photocurrent generation. However, this improvement in photocurrent generation is neutralized by a lower photovoltage as the apparent Fermi level of the TiO2and SWCNT composite becomes more positive than that of pristine TiO2.

The addition of potassium superoxide (KO2) into the electrolyte for Li-air battery was proved to be an effective screening method to examine the stability of the solvents against superoxide anion radicals (O2*[?]). It was also confirmed that the coupled compound between Li+ and O2*[?], namely LiO2*, was highly reactive for many solvents to decompose themselves. Specific ionic liquid and dimethylsulfoxide, selected solvents by the KO2 screening test, actually performed stable operation of Li-air battery.

Owing to their extremely high theoretical energy density, non-aqueous Li-air batteries have received remarkable attention in recent years. Ionic Liquids (ILs), molten salts that are liquid at room temperature, have been investigated as potential electrolytes in Li-air batteries due to their negligible vapor pressure, good thermal stability, and wide electrochemical windows. However, compared to conventional organic electrolytes, ILs generally have higher viscosity and, consequently, lower ionic conductivity and ion diffusivity. Therefore, we have selected eight low-viscosity ILs containing the bis(trifluoromethanesulfonyl)imide ([TFSI]-) anion, and their physical properties were characterized. The diffusivities of the cation and anion of the ILs were measured with pulsed-field-gradient spin-echo (PFG-SE) NMR Spectroscopy. In addition, the I-V performances of three characteristic ILs were tested in a Li-O2battery. The solubility of O2in the ILs and IL-Li[TFSI] mixtures, an additional property that can affect Li-air battery performance, was also measured using a gravimetric microbalance.

The addition of potassium superoxide (KO2) into the electrolyte for Li-air battery was proved to be an effective screening method to examine the stability of the solvents against superoxide anion radicals (O2•−). It was also confirmed that the coupled compound between Li+and O2•−, namely LiO2•, was highly reactive for many solvents to decompose themselves. Specific ionic liquid and dimethylsulfoxide, selected solvents by the KO2screening test, actually performed stable operation of Li-air battery.

The title battery exhibits a very high discharge capacity.

The effect of a hole transport layer on the photoelectrochemical responses from an organic solar cell consisting of a composite polymer film of 5,10,15,20-tetra(3-thienyl)-21H,23H-porphyrin and polythiophene was investigated. The polyalkylthiophene layer that was inserted between the above-described photoactive polymer film and a transparent electrode acted as the hole transport layer. This layer remarkably suppressed the recombination of separated charge carriers generated in the composite polymer film and substantially improved both photocurrent and conversion efficiencies.

The effect of a hole transport layer on the photoelectrochemical responses from an organic solar cell consisting of a composite polymer film of 5,10,15,20-tetra(3-thienyl)-21H,23H-porphyrin and polythiophene was investigated. The polyalkylthiophene layer that was inserted between the above-described photoactive polymer film and a transparent electrode acted as the hole transport layer. This layer remarkably suppressed the recombination of separated charge carriers generated in the composite polymer film and substantially improved both photocurrent and conversion efficiencies.