Lithium-air batteries are considered to be a potential alternative to lithium-ion batteries for transportation applications, owing to their high theoretical specific energy. So far, however, such systems have been largely restricted to pure oxygen environments (lithium-oxygen batteries) and have a limited cycle life owing to side reactions involving the cathode, anode and electrolyte. In the presence of nitrogen, carbon dioxide and water vapour, these side reactions can become even more complex. Moreover, because of the need to store oxygen, the volumetric energy densities of lithium-oxygen systems may be too small for practical applications. Here we report a system comprising a lithium carbonate-based protected anode, a molybdenum disulfide cathode and an ionic liquid/dimethyl sulfoxide electrolyte that operates as a lithium-air battery in a simulated air atmosphere with a long cycle life of up to 700 cycles. We perform computational studies to provide insight into the operation of the system in this environment. This demonstration of a lithium-oxygen battery with a long cycle life in an air-like atmosphere is an important step towards the development of this field beyond lithium-ion technology, with a possibility to obtain much higher specific energy densities than for conventional lithium-ion batteries.

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The controlled creation, manipulation and detection of spin-polarized currents by purely electrical means remains a central challenge of spintronics. Efforts to meet this challenge by exploiting the coupling of the electron orbital motion to its spin, in particular Rashba spin-orbit coupling, have so far been unsuccessful. Recently, it has been shown theoretically that the confining potential of a small current-carrying wire with high intrinsic spin-orbit coupling leads to the accumulation of opposite spins at opposite edges of the wire, though not to a spin-polarized current. Here, we present experimental evidence that a quantum point contact -- a short wire -- made from a semiconductor with high intrinsic spin-orbit coupling can generate a completely spin-polarized current when its lateral confinement is made highly asymmetric. By avoiding the use of ferromagnetic contacts or external magnetic fields, such quantum point contacts may make feasible the development of a variety of semiconductor spintronic devices.

Lithium-CO 2 batteries are attractive energy storage systems for fulfilling the demand of future large-scale applications such as electric vehicles due to their high specific energy density compared to lithium-ion batteries. However, a major challenge with Li-CO 2 batteries is attaining reversible formation and decomposition of the Li 2 CO 3 and carbon discharge products, along with a lack of mechanistic understanding of the associated charge and discharge reaction mechanisms. In this study, we developed a fully reversible Li-CO 2 battery with overall carbon neutrality using molybdenum disulfide nanoflakes as a cathode catalyst combined with an ionic liquid and dimethyl sulfoxide hybrid electrolyte. This combination of materials produces a multicomponent composite (Li 2 CO 3 /C) product rather than formation of separated carbon and Li 2 CO 3 nanoparticles. The battery shows a superior long cycle life of 500 for a fixed 500 mAh/g capacity per cycle, which is by far the best cycling stability reported in Li-CO 2 batteries, respectively. The long cycle life demonstrates for the first time that covalent CO bond making and breaking chemical transformations can be used in energy storage systems, in addition to the widely studied alkali metal (Li, Na, K)-oxygen ionic-bond making and breaking transformations. Theoretical calculations are used to deduce a mechanism for the reversible discharge/charge processes and explain how the carbon interface with Li 2 CO 3 provides the electronic conduction needed for the oxidation of Li 2 CO 3 , as well as the carbon to generate the CO 2 on charge. The achievement of a reversible, long cycle life Li-CO 2 battery opens the way for use of CO 2 in advanced energy storage systems. Lithium-ion batteries are widely used as electrochemical energy storage systems for consumer electronics [1] ; however, technologies with higher specific energy are needed for electrified transportation applications [2]. Therefore, beyond Li-ion battery chemistries such as rechargeable Li-O 2 batteries have recently garnered much attention This article is protected by copyright. All rights reserved. 3 due to their higher theoretical energy density [3,4]. Li-O 2 batteries generally have limited cyclability, though several studies have reported new concepts that have achieved long cycle life [5,6]. Although far less studied, the Li-CO 2 battery is another beyond Li-ion technology with a theoretical energy density of 1876 Wh/kg [7,8] , far exceeding that of Li-ion batteries (~265 Wh/kg). This type of battery involves CO 2 reduction and evolution reactions during discharge and charge, respectively, on the surface of a porous cathode with an electrolyte based on lithium salts.