Lithium sulfur (Li-S) batteries have drawn much attention as next-generation batteries because of their high theoretical capacity (1672 mAh g − 1), environmental friendliness and low cost. However, several critical issues, which are mainly associated with the polysulfide shuttling effect, result in their poor electrochemical performance. Carbon-modified separators have been introduced to attempt to address these systemic challenges. However, this approach focused only on the suppression of dissolved polysulfides on the cathodic side without considering the further entrapment of polysulfides on the anodic side. In this study, we first designed a multifunctional trilayer membrane comprising a carbon layer and a boron nitride (BN) layer to facilitate the electrochemical performance of Li-S batteries and protect the Li anode from unexpected side reactions. When a BN-carbon separator was employed, the sulfur cathode delivered stable capacity retention over 250 cycles and an excellent specific capacity (702 mAh g − 1) at a high current density (4 C). The BN-carbon separator also facilitated the uniform plating/striping of Li and, thus, suppressed the severe growth of dendritic Li on the electrode; this led to the stable operation of the Li anode with a high Coulombic efficiency and improved cycling performance.

It has been very difficult to remove smaller ceria particles from silicon dioxide surfaces. One of the likely reasons is that the smaller ceria particles with a higher surface concentration of Ce 3+ are more strongly coupled with silicon dioxide surfaces via strong Ce-O-Si bonding. Here, we show that some equimolar solutions containing H 2 O 2 and either NH 4 OH or KOH, aided by ultrasonic cleaning, and at high pH can almost completely remove even 10 nm sized ceria particles from silicon dioxide film surfaces. The particles on the oxide surface before and after cleaning were imaged using atomic force microscopy and counted. The optimal composition of H 2 O 2 -NH 4 OH solutions was identified by investigating ten solutions with different compositions using an augmented simplex-centroid method along with four H 2 O 2 -KOH solutions. Equimolar mixtures of H 2 O 2 and NH 4 OH or KOH with the highest possible perhydroxyl ion concentration [HO 2 − ] showed ∼99% cleaning efficiency for 10 nm ceria particles. We propose that the strong Ce-O-Si bonding can be ruptured effectively by the nucleophile HO 2 − , formed by the decomposition of H 2 O 2 in the high pH environment, and show that [HO 2 − ] is highest in equimolar solutions. The cleaning efficiencies for 10 nm, 30 nm and 90 nm particles correlate very nicely with [HO 2 − ].

Lithium-sulfur (Li-S) batteries have been intensively investigated as a next-generation rechargeable battery due to their high energy density of 2600 W·h kg(-1) and low cost. However, the systemic issues of Li-S batteries, such as the polysulfide shuttling effect and low Coulombic efficiency, hinder the practical use in commercial rechargeable batteries. The introduction of a conductive interlayer between the sulfur cathode and separator is a promising approach that has shown the dramatic improvements in Li-S batteries. The previous interlayer work mainly focused on the physical confinement of polysulfides within the cathode part, without considering the further entrapment of the dissolved polysulfides. Here, we designed an ultrathin poly(acrylic acid) coated single-walled carbon nanotube (PAA-SWNT) film as a synergic functional interlayer to address the issues mentioned above. The designed interlayer not only lowers the charge transfer resistance by the support of the upper current collector but also localizes the dissolved polysulfides within the cathode part by the aid of a physical blocking and chemical bonding. With the synergic combination of PAA and SWNT, the sulfur cathode with a PAA-SWNT interlayer maintained higher capacity retention over 200 cycles and achieved better rate retention than the sulfur cathode with a SWNT interlayer. The proposed approach of combining a functional polymer and conductive support material can provide an optimiztic strategy to overcome the fundamental challenges underlying in Li-S batteries.

Ceria nanoparticles (NPs) have been widely explored as a promising material in various fields. As synthesized under various physicochemical conditions, it exhibits the different surface chemistry. Here, the role of hydroxyl and nitrate group on ceria surface, formed under various physicochemical conditions, for the silicate adsorption was experimentally and theoretically investigated based on the adsorption isotherms and theoretical analyses using density functional theory (DFT) calculation. Experimental results acquired from adsorption isotherms with Freundlich model indicated that the nitrate group shows a much higher affinity with silicate than the hydroxyl groups. These phenomena were demonstrated through the theoretical approaches that exhibit the binding energy of the NO3-ceria (-4.383 eV) on the SiO2 surface being much higher than that of the OH-ceria (-3.813 eV). In good agreement with the experimental and the theoretical results based on adsorption properties, the results of chemical mechanical planarization (CMP) also show that the nitrate groups significantly enhance the removal of SiO2 than the hydroxyl groups. The results investigated in this study will provide researchers, studying the ceria NPs, with guidelines on the importance of exploring the surface chemistry of ceria.