on the redox chemistry of CO 2 , ideally following the equation 4Li + 3CO 2 ↔ 2Li 2 CO 3 + C with a theoretical energy density of 1876 Wh kg −1 . Li-CO 2 batteries represent a novel approach for the utilization of atmospheric CO 2 , and may potentially find applications where the CO 2 concentration is high, for example, in submarines or on Mars.Despite their great potential, many challenges would have to be overcome before Li-CO 2 batteries become a practical reality. The most serious one is the reversible electrochemical decomposition of Li 2 CO 3 at charge. It has been widely recognized from earlier Li-O 2 researches that the accumulation of Li 2 CO 3 on cathode from the parasitic reaction between CO 2 and Li 2 O 2 would passivate the electrode surface and gradually degrade the battery performance. [19][20][21][22] A high voltage (sometimes > 4.3 V versus Li/Li + ) is often required in order to decompose Li 2 CO 3 . Under such anodic potential, the electrolyte oxidation becomes significant. This problem escalates when it comes to Li-CO 2 batteries. We are in urgent need of efficient and robust cathode catalysts to facilitate the reversible Li 2 CO 3 formation and decomposition, promote the energy efficiency and enhance the cycle life. [14,15] Carbonaceous materials including pristine or doped graphene and carbon nanotubes were the first type of catalysts investigated for the Li-CO 2 application. [17,23,24] Despite the relative abundance and low cost, they generally fell short of expectations in terms of activity and stability. The charging overpotential was often observed to quickly rise with cycling. Very recently, Ru nanoparticles were revealed to promote Li 2 CO 3 decomposition: they lowered the charge voltage to 3.9 V and enabled an impressive cycle life. [16] Nevertheless, the high cost of Ru would obviously prohibit its large-scale application. It is therefore imperative to develop high-performance nonprecious metal-based cathode catalysts for Li-CO 2 batteries.One possible strategy is to search within the existing pool of catalyst materials for CO 2 reduction reaction (CO 2 RR) in aqueous solution. Even though the reaction pathways of CO 2 reduction in aqueous and aprotic media differ substantially, we believe that the knowledge accumulated on aqueous CO 2 RR can be used to inspire the Li-CO 2 research. Transition metal porphyrins and phthalocyanines have long been known for their CO 2 RR activities. [25,26] However, they are not naturally suited as the cathode catalyst of Li-CO 2 batteries owing to their Li-CO 2 batteries represent an attractive solution for electrochemical energy storage by utilizing atmospheric CO 2 as the energy carrier. However, their practical viability critically depends on the development of efficient and low-cost cathode catalysts for the reversible formation and decomposition of Li 2 CO 3 . Here, the great potential of a structurally engineered polymer is demonstrated as the cathode catalyst for rechargeable Li-CO 2 batteries. Conjugated cobalt polyphthalocyanine is prepared vi...

Even though advocated as the potential low-cost alternatives to current lithium-ion technology, the practical viability of sodium-ion batteries remains illusive and depends on the development of high-performance electrode materials. Very few candidates available at present can simultaneously meet the requirements on capacity, rate capability, and cycle life. Herein, we report a high-temperature solution method to prepare NiS nanorods with uniform sizes. These colloidal nanorods readily self-assemble side by side and form microsized superstructures, which unfortunately negates the nanoscale feature of individual nanorods. To this end, we further introduce two-dimensional graphene nanosheets as the spacer to interrupt nanorod self-assembly. Resultant composite presents a marked advantage toward electrochemical storage of Na ions. We demonstrate that in half-cells it exhibits large reversible specific capacity in excess of 600 mAh/g, high rate capability with >300 mAh/g retained at 4 A/g, and great cycle life at different current rates. This anode material can also be combined with the NASICON-type NaV(PO) cathode in full cells to enable large capacity and good cyclability.

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Monodisperse Cu2ZnSnS4 (CZTS) nanocrystals with tunable shape, crystalline phase, and composition are synthesized by efficient thermolysis of a single source precursor of mixed metal-oleate complexes in hot organic solvents with dissolved sulfur sources. Suitable tuning of the synthetic conditions and the Cu/(Zn + Sn) ratio of the precursor has enabled precise control of the crystalline phase in the form of kesterite, or a newly observed wurtzite structure. Nanocrystals with morphology in the form of spherical, rice-like, or rod-like shapes are obtained over a wide range of compositions (0.5 ≤ Cu/(Zn + Sn) ≤ 1.2). Both the final products and intermediates for each shape exhibit consistent composition and structure, indicating homogenous nucleation and growth of single-phase nanocrystals. Thin films prepared from colloidal nanocrystal suspensions display interesting shape-dependent photoresponse behavior under white light illumination from a solar simulator.