efficiency (CE) and cycling performance. [2] In addition, the lithium polysulfides dissolution and Li dendrite growth also require a large amount excess electrolyte to achieve high performance, thus reducing the energy density. Extensive efforts have been devoted to suppress "shuttle" of lithium polysulfide. Among them, encapsulating sulfur cathode into porous host materials including porous carbon, [3] metal oxide/chalcogenide, [4] and conductive polymers [5] are the most effective method for suppressing "shuttle" effect. On the Li anode side, nanostructure design [6] or surface modification [7] has been also developed to suppress the dendritic Li growth.Different from separately nanostructured design of the electrodes, rational design and optimization of electrolytes are more effective, [8] which simultaneously suppress both lithium polysulfide shuttle and Li dendrite. [9] Recently, highly concentrated electrolyte (HCE) systems with unique solvation structure and functionality have been successfully developed for high performance Li-S batteries. For example, Suo et al. showed a new class of ultrahigh salt concentration electrolyte, which can effectively suppress the lithium dendrite growth and inhibit the polysulfide shuttle phenomenon in Li-S batteries. [2c] Qian et al. reported that the high-concentration electrolytes enabled the high-rate cycling of lithium metal with a high CE up to 99.1% without dendrite growth. [2a] These significant performance improvements were contributed to the strong restraining property for the solvents from the high-concentrated salts in electrolyte that efficiently control the reaction dynamics and Li 2 S n solubility synchronously. These exciting breakthroughs demonstrated that such unique HCE systems can offer new possibilities to address the shuttle effect and dendritic Li growth efficiently and simultaneously.Nevertheless, the usage of a large amount of expensive lithium salt in the HCE systems also lead to several disadvantages, including high cost, poor wettability, high viscosity, and low ionic conductivity. [10] To address these issues without scarifying the unique characteristics of HCE, a new kind of localized high-concentration electrolyte (LHCE) was proposed by using a rational cosolvent dilution in HCE system. The choice of the cosolvent in LHCE is critical for the performance of Li-S batteries. In Li-S battery electrolytes, ether-based solvents with high donor number were usually employed, which can effectively dissociate the Li + from anion and dissolve Li salts. However, the strong donating ability of such solvents can also facilitate the dissolution of long-chain polysulfide and amplify Rechargeable Li-S batteries are regarded as one of the most promising next-generation energy-storage systems. However, the inevitable formation of Li dendrites and the shuttle effect of lithium polysulfides significantly weakens electrochemical performance, preventing its practical application. Herein, a new class of localized high-concentration electrolyte (LHCE) enabled ...

Piezocatalysis,converting mechanical vibration into chemical energy,h as emerged as ap romising candidate for water-splitting technology.H owever,t he efficiency of the hydrogen production is quite limited. We herein report welldefined 10 nm BaTiO 3 nanoparticles (NPs) characterized by al arge electro-mechanical coefficient which induces ah igh piezoelectric effect. Atomic-resolution high angle annular dark field scanning transmission electron microscopy(HAADF-STEM) and scanning probe microscopy(SPM) suggests that piezoelectric BaTiO 3 NPs displayac oexistence of multiple phases with lowe nergy barriers and polarization anisotropy which results in ahigh electro-mechanical coefficient. Landau free energy modeling also confirms that the greatly reduced polarization anisotropyf acilitates polarization rotation. Employing the high piezoelectric properties of BaTiO 3 NPs,w e demonstrate an overall water-splitting process with the highest hydrogen production efficiency hitherto reported, with aH 2 production rate of 655 mmol g À1 h À1 ,whichcould rival excellent photocatalysis system. This study highlights the potential of piezoelectric catalysis for overall water splitting.

Lithium–sulfur (Li–S) batteries are promising energy‐storage devices because of their high theoretical energy densities. However, the practical application of Li–S batteries is still impeded by the poor cycling performance and rate capability at practical conditions. In order to improve the performance of practical Li–S batteries, a hierarchical Mo2C nanocluster/carbon nanosheets hybrid based hollow spherical material (Mo2C/CHS) is designed and prepared. The hollow spheres composed of stacked carbon nanosheets can facilitate the infiltration of electrolyte. The ultrasmall and highly conductive Mo2C nanocrystals are confined in the carbon nanosheets and expose more active sites for anchoring and conversion of lithium polysulfides and increase the number of the nuclei for Li2S2/Li2S precipitation. Benefitting from the synergistic effects, Mo2C/CHS greatly promotes electrochemical kinetics in Li–S batteries with high sulfur loading (5 mg cm−2). Even under lean electrolyte conditions (E/S = 7 μL mgsulfur−1), the Li–S batteries with Mo2C/CHS added exhibit a discharge capacity of 904 mAh g−1 at the high current rate of 0.5 C, and with 894 mAh g−1 maintained after 200 cycles. This work provides a fundamental understanding of the electrochemical processes and guides the rational design of host and additive materials for practical Li–S batteries.

The rechargeable Zn−air batteries as an environmentally friendly sustainable energy technology have been extensively studied. However, it is still a challenge to develop non-noble metal bifunctional catalysts with high oxygen reduction as well as oxygen evolution reaction (ORR and OER) activity and superior durability, which limit the large-scale application of rechargeable Zn−air batteries. Herein, we synthesized an ultrastable FeCo bifunctional oxygen electrocatalyst on Se-doped CNTs (FeCo/Se-CNT) via a gravity guided chemical vapor deposition (CVD) strategy. The catalyst exhibits excellent ORR (E 1/2 = 0.9 V) and OER (overpotential at 10 mA cm −2 = 340 mV) properties simultaneously, surpassing commercial Pt/C and RuO 2 /C catalysts. More importantly, the catalyst shows an unordinary stability, that is, is no obvious decrease after 30K cycles accelerated durability test for ORR and OER processes. The small potential gap (0.75 V) represents superior bifunctional ORR and OER activities of the FeCo/ Se-CNT catalyst. The FeCo/Se-CNT catalyst possesses outstanding electrochemical performance for the rechargeable liquid and flexible all-solid-state Zn−air batteries, for example, a high open circuit voltage (OCV) and peak power density of 1.543 and 1.405 V and 173.4 and 37.5 mW cm −2 , respectively.

Developing a highly efficient, easy-to-fabricate and non-noble metal electrocatalyst is vital for oxygen reduction reaction (ORR). Herein, we fabricate a single Fe sites catalyst Fe1/d-CN by developing a double-layer MOF...