Self-assembled organic nanowires for high power density lithium ion batteries

The electroactive organic materials are promising alternatives to inorganic electrode materials for the new generation of green Li-ion batteries due to their sustainability, environmental benignity, and low cost. Croconic acid disodium salt (CADS) was used as Li-ion battery electrode, and CADS organic wires with different diameters were fabricated through a facile synthetic route using antisolvent crystallization method to overcome the challenges of low electronic conductivity of CADS and lithiation induced strain. The CADS nanowire exhibits much better electrochemical performance than its crystal bulk material and microwire counterpart. CADS nanowire with a diameter of 150 nm delivers a reversible capability of 177 mAh g(-1) at a current density of 0.2 C and retains capacity of 170 mAh g(-1) after 110 charge/discharge cycles. The nanowire structure also remarkably enhances the kinetics of croconic acid disodium salt. The CADS nanowire retains 50% of the 0.1 C capacity even when the current density increases to 6 C. In contrast, the crystal bulk and microwire material completely lose their capacities when the current density merely increases to 2 C. Such a high rate performance of CADS nanowire is attributed to its short ion diffusion pathway and large surface area, which enable fast ion and electron transport in the electrode. The theoretical calculation suggests that lithiation of CADS experiences an ion exchange process. The sodium ions in CADS will be gradually replaced by lithium ions during the lithiation and delithiation of CADS electrode, which is confirmed by inductively coupled plasma test.

Tuning the electrochemical performances of anthraquinone organic cathode materials for Li-ion batteries through the sulfonic sodium functional group

Na₂C₁₄H₆S₂O₈, which has a low dissolution in electrolyte with two modified SO₃Na– functional groups, exhibits excellent electrochemical performance.

Organic n-type materials for charge transport and charge storage applications

Conjugated materials have attracted much attention toward applications in organic electronics in recent years. These organic species offer many advantages as potential replacement for conventional materials (i.e., silicon and metals) in terms of cheap fabrication and environmentally benign devices. While p-type (electron-donating or hole-conducting) materials have been extensively reviewed and researched, their counterpart n-type (electron-accepting or electron-conducting) materials have seen much less popularity despite the greater need for improvement. In addition to developing efficient charge transport materials, it is equally important to provide a means of charge storage, where energy can be used on an on-demand basis. This perspective is focused on discussing a selection of representative n-type materials and the efforts toward improving their charge-transport efficiencies. Additionally, this perspective will also highlight recent organic materials for battery components and the efforts that have been made to improve their environmental appeal.

Functionalized graphene for high performance lithium ion capacitors

Lithium ion capacitors (LICs) have recently drawn considerable attention because they utilize the advantages of supercapacitors (high power) and lithium ion batteries (high energy). However, the energy densities of conventional LICs, which consist of a pair of graphite and activated carbon electrodes, are limited by the small capacities of the activated carbon cathodes. To overcome this limitation, we have engaged urea-reduced graphene oxide. The amide functional groups generated during the urea reduction facilitate the enolization processes for reversible Li binding, which improves the specific capacity by 37 % compared to those of conventional systems such as activated carbon and hydrazine-reduced graphene oxide. Utilizing the increased Li binding capability, when evaluated based on the mass of the active materials on both sides, the LICs based on urea-reduced graphene oxide deliver a specific energy density of approximately 106 Wh kg(total) (-1) and a specific power density of approximately 4200 W kg(total) (-1) with perfect capacity retention up to 1000 cycles. These values are far superior to those of previously reported LICs and supercapacitors, which suggests that appropriately treated graphene can be a promising electrode material for LICs.