Coupling quinone cathode with ionic liquid electrolyte is demonstrated to build high-energy and long-life sodium-ion batteries. Computational and spectroscopic studies reveal that the inhibitory effect of ionic liquid on dissolution of quinone correlates with the strong polarity, weak electron donor ability, and low interaction energy. The calix[4]quinone and 5,7,12,14-pentacenetetrone cathodes exhibit significantly improved cycling performance in N-methyl-N-propylpyrrolidinium bis(trifluoromethanesulfonyl)amide than in ether electrolyte. These results would enlighten the design and application of ionic liquid and quinones for organic batteries. HIGHLIGHTSA facile strategy is proposed to suppress the dissolution of quinone electrodes Inhibitory effect of ILs correlates to polarity, donor number, and binding energy [PY13][TFSI] markedly inhibits quinone dissolution C4Q and PT cathodes exhibit better capacity retention in ILs than in ether Wang et al., Chem 5, 364-375 February 14, SUMMARYQuinone-based sodium-ion batteries (SIBs) are highly desirable electrochemical devices with high capacity and low cost but suffer from poor cycle life and low practical energy because of quinone dissolution in aprotic electrolyte. Herein, we report a facile strategy of using ionic liquid (IL) to tackle the dissolution of quinone electrodes. The inhibitory effect of ILs on quinone dissolution correlates with their polarity, donor number, and interaction energy, as revealed by combined density functional theory and spectroscopy studies. Particularly, in N-methyl-N-propylpyrrolidinium bis(trifluoromethanesulfonyl)amide ([PY13] [TFSI]) electrolyte with weak donor ability and large polarity, calix[4]quinone cathode exhibits high capacity (>400 mAh g À1 ) and superior capacity retention ($99.7% at 130 mA g À1 for 300 cycles), significantly outperforming that in etherbased electrolyte. Moreover, the remarkable cyclability and considerable rate capability of 5,7,12,14-pentacenetetrone in [PY13][TFSI] render it a promising sodium-storage material. This work would promote the development of highperformance SIBs with quinone electrodes and IL electrolyte.

Electrochemical energy storage with redox-flow batteries (RFBs) under subzero temperature is of great significance for the use of renewable energy in cold regions. However, RFBs are generally used above 10 °C. Herein we present non-aqueous organic RFBs based on 5,10,15,20-tetraphenylporphyrin (H TPP) as a bipolar redox-active material (anode: [H TPP] /H TPP, cathode: H TPP/[H TPP] ) and a Y-zeolite-poly(vinylidene fluoride) (Y-PVDF) ion-selective membrane with high ionic conductivity as a separator. The constructed RFBs exhibit a high volumetric capacity of 8.72 Ah L with a high voltage of 2.83 V and excellent cycling stability (capacity retention exceeding 99.98 % per cycle) in the temperature range between 20 and -40 °C. Our study highlights principles for the design of RFBs that operate at low temperatures, thus offering a promising approach to electrochemical energy storage under cold-climate conditions.

This work is pioneering to introduce molecular electrostatic potential (MESP) to investigate the interaction between lithium ions and organic electrode molecules. The electrostatic potential on the van der Waals surface of the electrode molecule is calculated, and then the coordinates and relative values of the local minima of MESP can be correlated to the Li binding sites and sequence on an organic small molecule, respectively. This suggests a gradual lithiation process. Similar calculations are extended to polymers and even organic crystals. The operation process of MESP for these systems is explained in detail. Through providing accurate and visualizable lithium binding sites, MESP can give precise prediction of the lithiated structures and reaction mechanism of organic electrode materials. It will become a new theoretical tool for determining the feasibility of organic electrode materials for alkali metal ion batteries.

The rearrangements between the closed [6,6] and open [5,6] isomers of C60O, as well as the closed [6,6], closed [5,6], and open [5,6] isomers of C60S have been studied using semiempirical AM1 and MNDO methods. The results show that the interconversion of the two isomers of C60O follows a two-step pathway involving an intermediate and two transition states. The calculated activation barriers for the migration of oxygen from [6,6]-bond to [5,6]-bond through an intermediate are 189.1 and 54.6 kJ mol-1, respectively. In the opposite way, the calculated activation barriers for the migration of oxygen from [5,6]-bond to [6,6]-bond through an intermediate are 293.2 and 2.7 kJ mol-1, respectively. The interconversion of the closed [6,6] and the open [5,6] isomers of C60S also follows a stepwise pathway via a local energy minimum corresponding to the closed [5,6] isomer. The calculated activation barriers for the migration of sulfur from [6,6]-bond to [5,6]-bond (in open [5,6] isomer) through the closed [5,6] isomer are 233.2 and 1.2 kJ mol-1, respectively. In the opposite way, the calculated activation barriers for the migration of sulfur from [5,6]-bond (in open [5,6] isomer) to [6,6]-bond via the closed [5,6] isomer are 82.0 and 150.5 kJ mol-1, respectively. The large barriers suggested that it should be possible to isolate the closed [6,6] and open [5,6] isomers of C60O at room temperature. This is consistent with experimental results. In addition, it can be inferred from our results that rearrangement between the two isomers of C60O can take place under heating or lighting conditions. Meanwhile, it can be deduced from our results that it should be possible to isolate both the closed [6,6] and the open [5,6] isomers of C60S at room temperature and to convert one into the other when certain energy is offered. It seems that the closed [5,6] isomer of C60S may not be observed experimentally at room temperature.

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