A Step-by-Step Design Strategy to Realize High-Performance Lithium-Sulfur Batteries

In order to increase the energy density and improve the cyclability of lithium-sulfur (Li-S) batteries, a combined strategy is devised and evaluated for high-performance Li-S batteries. It consists of the following steps to reduce the loss of active sulfur and sulfides migrating in the liquid electrolyte to the anode and add electrocatalyst groups in the cathode or catholyte: (i) A hollow porous nanoparticle coating cathode host with a pseudocapacitive PEDOT:PSS binder that also contributes to trapping polysulfides. (ii) A thin interlayer of B-N-graphene (BNG) nanoplatelets on the above cathode trapping polysulfides while participating in the electron transfer and acting as an electrocatalyst, thus ensuring that the trapped sulfides remain active in the cathode. (iii) Added semiconductor phthalocyanine VOPc or CoPc to form an electrocatalyst network in the catholyte, trapping polysulfides and promoting their redox reactions with Li+ ions. (iv) Added silk fibroin in the liquid electrolyte, which also suppresses dendritic growth on the lithium anode. This strategy is evaluated step-by-step in Li-S battery cells characterized experimentally and in simulations based on a multipore continuum physicochemical model with adsorption energy data supplied from molecular dynamics simulations. The thin BNG interlayer sprayed on the cathode proved a decisive factor in improving cell performance in all cases. A Li-S cell combining features from (i), (ii), and (iv) and with 45 wt % S in the cathode yields 1372 mAh gS -1 at first discharge and 920 mAh gS -1 at the 100th discharge after a cycling schedule at different C-rates. A Li-S cell combining features from (i), (ii), and (iii) and with 55 wt % S in the cathode yields 805 and 586 mAh gS -1 at the first and the 100th discharge, respectively.

Recent Advances in Hole-Transporting Layers for Organic Solar Cells

Global energy demand is increasing; thus, emerging renewable energy sources, such as organic solar cells (OSCs), are fundamental to mitigate the negative effects of fuel consumption. Within OSC's advancements, the development of efficient and stable interface materials is essential to achieve high performance, long-term stability, low costs, and broader applicability. Inorganic and nanocarbon-based materials show a suitable work function, tunable optical/electronic properties, stability to the presence of moisture, and facile solution processing, while organic conducting polymers and small molecules have some advantages such as fast and low-cost production, solution process, low energy payback time, light weight, and less adverse environmental impact, making them attractive as hole transporting layers (HTLs) for OSCs. This review looked at the recent progress in metal oxides, metal sulfides, nanocarbon materials, conducting polymers, and small organic molecules as HTLs in OSCs over the past five years. The endeavors in research and technology have optimized the preparation and deposition methods of HTLs. Strategies of doping, composite/hybrid formation, and modifications have also tuned the optical/electrical properties of these materials as HTLs to obtain efficient and stable OSCs. We highlighted the impact of structure, composition, and processing conditions of inorganic and organic materials as HTLs in conventional and inverted OSCs.