One-pot conversion of carbon dioxide to CNT-grafted graphene bifunctional for sulfur cathode and thin interlayer of Li–S battery

CO2-Derived Nanocarbons with Controlled Morphology and High Specific Capacitance

The conversion of CO2 to nanocarbons addresses a dual goal of harmful CO2 elimination from the atmosphere along with the production of valuable nanocarbon materials. In the present study, a simple one-step metallothermic CO2 reduction to nanocarbons was performed at 675 °C with the usage of a Mg reductant. The latter was employed alone and in its mixture with ferrocene, which was found to control the morphology of the produced nanocarbons. Scanning electron microscopy (SEM) analysis reveals a gradual increase in the amount of nanoparticles with different shapes and a decrease in tubular nanostructures with the increase of ferrocene content in the mixture. A possible mechanism for such morphological alterations is discussed. Transmission electron microscopy (TEM) analysis elucidates that the nanotubes and nanoparticles gain mainly amorphous structures, while sheet- and cloud-like morphologies also present in the materials possess significantly improved crystallinity. As a result, the overall crystallinity was preserved constant for all of the samples, which was confirmed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) techniques. Finally, electrochemical tests demonstrated that the prepared nanocarbons retained high specific capacitance values in the range of 200-310 F/g (at 0.1 V/s), which can be explained by the measured high specific surface area (650-810 m2/g), total pore volume (1.20-1.55 cm3/g), and the degree of crystallinity. The obtained results demonstrate the suitability of ferrocene for managing the nanocarbons' morphology and open perspectives for the preparation of efficient "green" nanocarbon materials for energy storage applications and beyond.

Recent Development in Novel Lithium-Sulfur Nanofiber Separators: A Review of the Latest Fabrication and Performance Optimizations

Lithium-Sulfur batteries (LSBs) are one of the most promising next-generation batteries to replace Li-ion batteries that power everything from small portable devices to large electric vehicles. LSBs boast a nearly five times higher theoretical capacity than Li-ion batteries due to sulfur's high theoretical capacity, and LSBs use abundant sulfur instead of rare metals as their cathodes. In order to make LSBs commercially viable, an LSB's separator must permit fast Li-ion diffusion while suppressing the migration of soluble lithium polysulfides (LiPSs). Polyolefin separators (commonly used in Li-ion batteries) fail to block LiPSs, have low thermal stability, poor mechanical strength, and weak electrolyte affinity. Novel nanofiber (NF) separators address the aforementioned shortcomings of polyolefin separators with intrinsically superior properties. Moreover, NF separators can easily be produced in large volumes, fine-tuned via facile electrospinning techniques, and modified with various additives. This review discusses the design principles and performance of LSBs with exemplary NF separators. The benefits of using various polymers and the effects of different polymer modifications are analyzed. We also discuss the conversion of polymer NFs into carbon NFs (CNFs) and their effects on rate capability and thermal stability. Finally, common and promising modifiers for NF separators, including carbon, metal oxide, and metal-organic framework (MOF), are examined. We highlight the underlying properties of the composite NF separators that enhance the capacity, cyclability, and resilience of LSBs.

An Ultra-Long-Life Flexible Lithium-Sulfur Battery with Lithium Cloth Anode and Polysulfone-Functionalized Separator

Flexible and high-performance batteries are urgently required for powering flexible/wearable electronics. Lithium-sulfur batteries with a very high energy density are a promising candidate for high-energy-density flexible power source. Here, we report flexible lithium-sulfur full cells consisting of ultrastable lithium cloth anodes, polysulfone-functionalized separators, and free-standing sulfur/graphene/boron nitride nanosheet cathodes. The carbon cloth decorated with lithiophilic three-dimensional MnO₂ nanosheets not only provides the lithium anodes with an excellent flexibility but also limits the growth of the lithium dendrites during cycling, as revealed by theoretical calculations. Commercial separators are functionalized with polysulfone (PSU) via a phase inversion strategy, resulting in an improved thermal stability and smaller pore size. Due to the synergistic effect of the PSU-functionalized separators and boron nitride-graphene interlayers, the shuttle of the polysulfides is significantly inhibited. Because of successful control of the shuttle effect and dendrite formation, the flexible lithium-sulfur full cells exhibit excellent mechanical flexibility and outstanding electrochemical performance, which shows a superlong lifetime of 800 cycles in the folded state and a high areal capacity of 5.13 mAh cm^-2. We envision that the flexible strategy presented herein holds promise as a versatile and scalable platform for large-scale development of high-performance flexible batteries.

Lithium-Sulfur Batteries: Advances and Trends

A review with 132 references. Societal and regulatory pressures are pushing industry towards more sustainable energy sources, such as solar and wind power, while the growing popularity of portable cordless electronic devices continues. These trends necessitate the ability to store large amounts of power efficiently in rechargeable batteries that should also be affordable and long-lasting. Lithium-sulfur (Li-S) batteries have recently gained renewed interest for their potential low cost and high energy density, potentially over 2600 Wh kg−1. The current review will detail the most recent advances in early 2020. The focus will be on reports published since the last review on Li-S batteries. This review is meant to be helpful for beginners as well as useful for those doing research in the field, and will delineate some of the cutting-edge adaptations of many avenues that are being pursued to improve the performance and safety of Li-S batteries.

Ni12P5 nanoparticles bound on graphene sheets for advanced lithium-sulfur batteries

Lithium-sulfur batteries (LSBs) have been regarded as potential energy storage devices by virtue of their high theoretical capacity, natural abundance of materials and low cost. However, the notorious shuttle effect and sluggish reaction kinetics are still significant challenges for further development. Herein, Ni₁₂P₅ nanoparticles are devised and grown on a reduced graphene oxide (Ni₁₂P_5@rGO) framework via a self-template and recrystallization-self-assembly strategy, as the modifier for separators in LSBs for the first time. The support of rGO for Ni₁₂P₅ nanoparticles could solve the self-aggregation problem. Ni₁₂P₅ nanoparticles not only effectively adsorb polysulfides by polar interaction, but also supply active sites to ameliorate the kinetics of the redox reaction of sulfur. Consequently, when a sulfur-containing commercial acetylene black material (70 wt% sulfur content) is used as the cathode composite without complicated fabrication or surface modification, an LSB with Ni₁₂P₅@rGO modified separator shows excellent cycling stability and a capacity degradation of 0.074% per cycle at the current density of 1 C for 500 cycles. When the areal mass of sulfur further increases to 3.5 mg cm^-2, the capacity degradation is only 0.071% per cycle at 150 cycles. This study could accelerate the application of phosphides in LSBs.