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Abstract: Host materials that can provide both a strong absorbability of soluble intermediate polysulfides and a high electronic conductivity are in high demand to realize practical applications of Li–S batteries. Here, the rational design of an N‐doped carbon comb (NCC) as a new type of sulfur host for Li–S batteries, delivering a favorable performance, particularly a good cycling stability and rate capability, is reported. A novel dodecylamine micelle‐induced self‐assembling method is first proposed for constructing the NCC host which is built from close‐packed hollow submicron carbon spheres. The interconnected carbon frameworks create good electrical conductive pathways. In addition, the high porosity and the N doping of the NCC host effectively suppress sulfur losses during cycling through synergistic physisorption and chemisorption effects. As a result, cathodes with 71 wt% of sulfur deposited in the NCC host possess superior capacities of 1090 and 553 mAh g−1 at 0.1 and 2 C, respectively. After 300 cycles at 1 C, a reversible capacity of 562 mAh g−1 is retained. Even at a high sulfur loading of 83 wt%, favorable performance is realized. [ABSTRACT FROM AUTHOR]

A sponge-like V2O5 nanomaterial is prepared by a freeze-drying method and evaluated as a cathode material for sodium-ion batteries. The sponge-like structure is self-assembled from V2O5 nanosheets that can sustain high pressure (400 times their own weight), thus leading to a high structure stability. The numerous macropores in the spongy structure can effectively soak up the electrolyte. Moreover, the exposed (001) facet of the nanosheets is favorable for charge transfer at the electrolyte/electrode interface. The thin nanosheets along the [001] axis provide short diffusion pathways for sodium ions. Electrochemical experiments show that the material has a high discharge capacity of 216 mAh g−1 at a current density of 20 mA g−1. In addition, the material shows a good capacity retention of 73 % in 100 charge-discharge cycles at a current density of 100 mA g−1. [ABSTRACT FROM AUTHOR]

Hierarchically porous, metallic RuO2 hollow spheres are applied as a carbon‐free cathode for Li–O2 batteries for the first time. They exhibit low charge potentials of ≈3.5 V, corresponding to overpotentials of 0.13/0.54 V in discharging and charging processes, a large reversible capacity of ≈1400 mAh g−1, and 100 cycles of full discharge and charge. [ABSTRACT FROM AUTHOR]

Porous carbon-free cathodes are critical to achieve a high discharge capacity and efficient cycling for rechargeable Li-O2 battery. Herein, we present a very simple method to directly grow nanoporous Ru (composed of polycrystalline particles of ∼5 nm) on one side of a current collector of Ni foam via a galvanic replacement reaction. The resulting Ru@Ni can be employed as a carbon- and binder-free cathode for Li-O2 batteries and delivers a specific capacity of 3720 mAh gRu−1 at a current density of 200 mA gRu−1. 100 cycles of continuous discharge and charge are obtained at a very narrow terminal voltage window of 2.75∼3.75 V with a limited capacity of 1000 mAh gRu−1. The good performance of the nanoporous Ru@Ni cathode can be mainly attributed to the effective suppression of the by-products related to carbon or binder, the good adhesion of the catalyst to the current collector, and the good permeation of O2 and electrolyte into the active sites of the nanoporous Ru with the open pore system. This new type electrode provides a snapshot toward developing high-performance carbon- and binder-free Li-O2 batteries. [ABSTRACT FROM AUTHOR]

Abstract Poor electrical conductivity of sulfur, sluggish redox kinetics, dissolution of intermediate polysulfides, and expansion in volume upon cycling are the main drawbacks that hamper the practical application of Li-S batteries. By taking advantages of the high conductivity and favorable catalytic activity of RuO 2 , we design a 3D carbon nanotube film with embedded RuO 2 nanoparticles as a freestanding type of chemisorptive and catalyst-like cathode for Li-S batteries, which can be facilely prepared by a surfactant-assisted vacuum infiltration method. Both experimental and theoretical results reveal the excellent capability of RuO 2 for anchoring polysulfides and accelerating the kinetics of polysulfides catalytic redox reactions. Besides, the 3D freestanding cathode is beneficial to overcoming pulverization during volume changes, especially for long-term cycling. At a high areal sulfur loading of 2 mg cm−2, favorable initial capacities of 750 and 1060 mA h g−1 respectively at 2 and 0.5 C are achieved. More attractively, the capacity after 1000 cycles maintains 405 mA h g−1 at 0.5 C with a loss in capacity of only 0.06% per cycle. Additionally, such freestanding cathode allows the batteries to be tested under various bending stages, hence encouraging more research works on fabrication of other 3D nanostructure families as high-performance cathodes for Li-S batteries. Graphical abstract A 3D free-standing catalyst-like cathode is designed and prepared for Li-S battery through a surfactant-assisted infiltration approach. Favorable high-rate performances and stabilities are delivered for Li-S battery with the as-prepared cathode due to the excellent chemisorption, high conductivity and for various redox reactions of RuO 2. The 3D free-standing catalyst-like cathode provides an inspirational model for promising flexible energy storage devices. Image 1 Highlights • A free-standing porous RuO 2 -embedded 3D CNT film is fabricated. • The freestanding film can overcome the pulverization of sulfur cathode. • Conductive RuO 2 shows favorable catalytic activity for polysulfides. • The cross-linked CNT enables the electron transport in whole cathode. • The Li-S battery with the freestanding cathode operates over 1000 cycles. [ABSTRACT FROM AUTHOR]

A sol-gel method with ethylene diamine tetraacetic acid and citric acid as co-chelates is employed for the synthesis of P2-type Na 2/3 Mn 1/2 Fe 1/4 Co 1/4 O 2 as cathode material for sodium-ion batteries. Among the various calcination temperatures, the Na 2/3 Mn 1/2 Fe 1/4 Co 1/4 O 2 with a pure P2-type phase calcined at 900 °C demonstrates the best cycle capacity, with a first discharge capacity of 157 mA h g −1 and a capacity retention of 91 mA h g −1 after 100 cycles. For comparison, the classic P2-type Na 2/3 Mn 1/2 Fe 1/2 O 2 cathode prepared under the same conditions shows a comparable first discharge capacity of 150 mA h g −1 but poorer cycling stability, with a capacity retention of only 42 mA h g −1 after 100 cycles. Based on X-ray photoelectron spectroscopy, the introduction of cobalt together with sol-gel synthesis solves the severe capacity decay problem of P2-type Na 2/3 Mn 1/2 Fe 1/2 O 2 by reducing the content of Mn and slowing down the loss of Mn on the surface of the Na 2/3 Mn 1/2 Fe 1/4 Co 1/4 O 2 , as well as by improving the activity of Fe 3+ and the stability of Fe 4+ in the electrode. This research is the first to demonstrate the origin of the excellent cycle stability of Na 2/3 Mn 1/2 Fe 1/4 Co 1/4 O 2 , which may provide a new strategy for the development of electrode materials for use in sodium-ion batteries. [ABSTRACT FROM AUTHOR]

Considering the abundance and low price of sodium, sodium-ion batteries (SIBs) are of particular attractiveness for large-scale electrochemical energy storage. Layered P2–Na 2/3 Mn 1/2 Fe 1/4 Co 1/4 O 2 (NMFC) is a promising cathode material for SIBs because of its large theoretical capacity, however, its high air sensitivity and poor cycling stability seriously limits the practical use. Here, we report nanometre-thick Al 2 O 3 coating of NMFC electrode through atomic layer deposition (ALD) technique can effectively alleviate such deficiencies to obtain an air-insensitive electrode, which was realized by effectively preventing the direct exposure of NMFC to H 2 O and CO 2 present in the air atmosphere. Interestingly, the ultrathin Al 2 O 3 coating did not cause a block for sodium ion intercalation, and a high capacity of 217.9 mA h g−1 at a high cut-off potential of 4.5 V was achieved. More attractively, a capacity retention rate as high as 84.8% was obtained after cycling at a current density of 0.5C over 100 cycles, demonstrating improved electrochemical stability. Based on CV and EIS characterizations, such good cycling stability is associated with the use of the Al 2 O 3 coating layer as well, which effectively avoided the side reactions at the interface of the liquid electrolyte and the active material under high potential. Display Omitted • Layered P2-type Na 2/3 Mn 1/2 Fe 1/4 Co 1/4 O 2 (NMFC) oxide was synthesized by solid-state method. • Ultrathin Al 2 O 3 layer was successfully coated on NMFC by atomic layer deposition. • The air sensitivity of NMFC was reduced. • The cycling stability of NMFC was improved. [ABSTRACT FROM AUTHOR]