In-situ synthesis Fe3C@C/rGO as matrix for high performance lithium-sulfur batteries at room and low temperatures.

People have been focusing on how to improve the specific capacity and cycling stability of lithium-sulfur batteries at room temperature, however, on some special occasions such as cold cities and aerospace fields, the operating temperature is low, which dramatically hinders the performance of batteries. Here, we report an iron carbide (Fe3C)/rGO composite as electrode host, the Fe3C nanoparticles in the composite have strong adsorption and high catalytic ability for polysulfide. The rGO makes the distribution of Fe3C nanoparticles more disperse, and this specific structure makes the deposition of Li2S more uniform. Therefore, it realizes the rapid transformation and high performance of lithium-sulfur batteries at both room and low temperatures. At room temperature, after 100 cycles at 1C current density, the reversible specific capacity of the battery can be stabilized at 889 ± 7.1 mAh/g. Even at -40 °C, in the first cycle battery still emits 542.9 ± 3.7 mAh/g specific capacity. This broadens the operating temperature for lithium-sulfur batteries and also provides a new idea for the selection of host materials for sulfur in low-temperature lithium-sulfur batteries.

Synthesis of Low-Cost and High-Performance Dual-Atom Doped Carbon-Based Materials with a Simple Green Route as Anodes for Sodium-Ion Batteries.

Sodium-ion batteries (SIBs) are promising alternatives to replace lithium-ion batteries as future energy storage batteries because of their abundant sodium resources, low cost, and high charging efficiency. In order to match the high energy capacity and density, designing an atomically doped carbonous material as the anode is presently one of the important strategies to commercialize SIBs. In this work, we report the preparation of high-performance dual-atom-doped carbon (C) materials using low-cost corn starch and thiourea (CH4N2S) as the precursors. The electronegativity and radii of the doped atoms and C are different, which can vary the embedding properties of sodium ions (Na+) into/on C. As sulfur (S) can effectively expand the layer spacing, it provides more channels for embedding and de-embedding Na+. The synergistic effect of N and S co-doping can remarkably boost the performance of SIBs. The capacity is preserved at 400 mAh g -1 after 200 cycles at 500 mA g-1; more notably, the initial Coulombic efficiency is 81%. Even at a high rate of high current of 10 A g-1, the cell capacity can still reach 170 mAh g-1. More importantly, after 3000 cycles at 1 A g-1, the capacity decay is less than 0.003% per cycle, which demonstrates its excellent electrochemical performance. These results indicate that high-performance carbon materials can be prepared using low-cost corn starch and thiourea.

Thin Nano Cages with Limited Hollow Space for Ultrahigh Sulfur Loading Lithium-Sulfur Batteries.

Owning to its various advantages, the lithium-sulfur battery is one of the research hot spots for new energy storage systems. Diverse hollow structures with specific morphologies have been used as the sulfur host materials to adsorb or/and catalyze the polysulfides, and can in particular concurrently inhibit the volume expansion during electrochemical processes in lithium-sulfur batteries. However, hollow space with a large volume will restrict the performance of the cell under high sulfur area loading, which is a very important indicator for the practical applications of the lithium-sulfur battery. Here, we report a nano thin cage cobalt acid zinc (ZnCo2O4) with limited hollow space as the cathode catalyst for lithium-sulfur batteries, which greatly reduces the electrode volume occupied by the hollow structure. The hollow volume of these thin cages is much smaller than those of the normally reported hollow materials in the literatue. The electrochemical performance of lithium-sulfur batteries with ZnCo2O4 thin cages could greatly improve due to the unique structure and the synergistic adsorption/catalytic effect of Zn/Co sites, especially at an ultrahigh S area load. Under a high S loading of 8 mg cm-2, the cell could keep a reversible capacity of 600 mAh g-1 after 500 cycles. Even at a sulfur loading of 10 mg cm-2, the cell still releases a discharge capacity of 1000 mAh g-1 which is equivalent of an area capacity of 10 mAh cm-2. This work provides a feasible way to develop lithium sulfur batteries with a high area sulfur load. This idea provides a possible solution to develop a Li-S battery at high area S loading and move one step closer to the practical applications.