Elemental sulfur is one of the most attractive cathode active materials in lithium batteries because of its high theoretical specific capacity. Despite the positive aspect, lithium–sulfur batteries have suffered from severe capacity fading and limited rate capability. Here we report facile large-scale synthesis of a class of organosulfur compounds that could open a new chapter in designing cathode materials to advance lithium–sulfur battery technologies. Porous trithiocyanuric acid crystals are synthesized for use as a soft template, where the ring-opening polymerization of elemental sulfur takes place along the thiol surfaces to create three-dimensionally interconnected sulfur-rich phases. Our lithium–sulfur cells display discharge capacity of 945 mAh g−1 after 100 cycles at 0.2 C with high-capacity retention of 92%, as well as lifetimes of 450 cycles. Particularly, the organized amine groups in the crystals increase Li+-ion transfer rate, affording a rate performance of 1210, mAh g−1 at 0.1 C and 730 mAh g−1 at 5 C.

We report the facile synthesis of new naphthoquinone (NQ) derivatives for use in lithium-organic batteries to improve performance. The rational design of these NQ derivatives is based on theoretical calculations. Our lithium-organic batteries demonstrate remarkable charge− discharge properties, for example, a high discharge capacity of 250 mAh g −1 (363 mAh cm −3 ), discharge potential plateaus in the range of 2.3−2.5 V, and 99% capacity retention after 500 cycles at 0.2C. In particular, the batteries had excellent rate performance up to 50C with reversible redox behavior, unlike most other organic cathode materials. The key to success was a simple molecular substitution, addition of amino groups at the 2-and 3-positions of the NQ ring, yielding 2,3-diamino-1,4naphthoquinone (DANQ). DANQ has an exceptionally low band gap of 2.7 eV and greater than 20-fold enhancement in the lithium diffusion rate compared to unmodified NQ. The fundamental shortcoming of the organic molecules, i.e., their solubility in the electrolyte, was resolved by covalent linking of the amino groups to the surfaces of the cathode framework. The cyclization of amino groups in DANQ yielded 1H-naphtho[2,3-d]imidazole-4,9-dione (IMNQ), enabled us to achieve a 0.15 V enhancement in the redox potential owing to the delocalized electron distribution in the heteroaromatic ring. Our work suggests that NQ derivatives with modulated charge/ion transport properties are a viable alternative to the more widely studied lithium metal oxides.

organic cathode materials that are sustainable and environmentally friendly.Carbonyl compounds, i.e., quinones, are especially appealing in this regard, owing to their special advantages such as fast reaction kinetics and high theoretical gravimetric capacities. [8,9,[23][24][25] The theoretical specific capacity of 1,4-benzoquinone is 496 mA h g −1 , [25] which surpasses that of commercial lithium cobalt oxide (272 mA h g −1 ). [26] A body of literature on quinones has further shown the possibility of tailoring their charge transport properties (redox potentials, lithium diffusivity, and so on) at the molecular level through the modification of the ring structure to achieve desired electrochemical performance. [24,[27][28][29][30][31][32][33] Nevertheless, over the last few decades only a limited number of naturally derived quinones have been actually investigated, such as juglone [17] and emodin. [18] The development of true green organic cathodes seems distant. Moreover, most quinones (and other organic compounds) have been plagued by poor electrical and ionic conductivities, [13,34,35] precluding the corresponding lithium batteries from approaching their theoretical capacities. [35][36][37] The solution to this problem has not been established until recently.Here, we report achieving high electrical and ionic conductivities in organic cathode materials by using lawsone (2-hydroxy-1,4-naphthoquinone), another naturally derived quinone. Lawsone is a red-orange dye present in the leaves of the henna plant (Lawsonia inermis), and has long been used on human hair and skin (temporary tattoo). Two other synthetic quinones were used as controls: menadione (also called vitamin K 3 , 2-methyl-1,4-naphthoquinone) that is occasionally used as a nutritional supplement, and 1,4-naphthoquinone (NQ).The electrical/ionic conductivities of lawsone are demonstrated to be up to several orders of magnitude higher than those of menadione and NQ. Based on a fundamental understanding of charge transport in single crystal samples, such improvement can be rationalized by the 2D planar packing of lawsone molecules with short stacking distance and overlapping adjacent p orbitals. Lithium batteries based on the lawsone cathode can deliver a high discharge capacity of 280 mA h g −1 (theoretical value: 283 mA h g −1 ) with 99% capacity retention after 1000 cycles at 0.5 C, along with excellent rate capability. 2-hydroxy-1,4-naphthoquinone), a naturally derived red-orange dye, is investigated as a promising cathode material for next-generation lithium batteries. Lithium cells based on lawsone cathode display a high discharge capacity of 280 mA h g −1 (99% theoretical capacity), a high energy density of 664 W h kg −1 , and long life of 1000 cycles at 0.5 C along with good rate performance up to 5 C. These results represent significant improvements from previously reported organic cathode materials, and surpass those of conventional lithium batteries based on LiCoO 2 cathodes (140 mA h g −1 and 520 W h kg −1 , respectively). Its success stems...

Triptycene bearing three benzoquinone moieties in a rigid 3-D tripod structure is capable of utilizing five-electron redox reactions that can provide a large capacity and high energy density in Li-ion cells.

A new method to develop two-dimensional PANI nanosheets using ice as a removable hard template is presented. Distinctly high current flows of 5.5 mA at 1 V and a high electrical conductivity of 35 S cm(-1) were obtained for the polyaniline (PANI) nanosheets, which marked a significant improvement from previously values on other PANIs reported over the past decades. These improved electrical properties of ice-templated PANI nanosheets were attributed to the long-range ordered edge-on π-stacking of the quinoid ring, ascribed to the ice surface-assisted vertical growth of PANI. The unprecedented advantages of the ice-templated PANI nanosheets are two-fold. First, the PANI nanosheet can be easily transferred onto various types of substrates via float-off from the ice surfaces. Second, PANI can be patterned into any shape using predetermined masks, and this is expected to facilitate the eventual convenient and inexpensive application of conducting polymers in versatile electronic device forms.