Search

A sufficient areal capacity is necessary for achieving high-energy lithium–sulfur batteries, which require sufficiently high sulfur loading in the cathode materials. Therefore, the kinetically fast catalytic conversion of polysulfide intermediates is especially important for the full utilization of sulfur. Herein, Co9S8−x/N-doped graphene (Co9S8−x/N-G) is used as a sulfur host material and electrocatalyst in a high-sulfur-loading cathode, in which sulfur vacancies are generated via the hydrogen reduction of stoichiometric Co9S8. The produced sulfur vacancies in Co9S8−x/N-G effectively improve the adsorption ability for polysulfide anions, and theoretical calculations indicate that Co9S8−x has lower adsorption energy for polysulfides than Co9S8. Furthermore, electrochemical experiments reveal that the electrode process kinetics for the catalytic conversion of polysulfides are enhanced by sulfur vacancies. As a result, the S/Co9S8−x/N-G cathode with a high sulfur loading of 14.6 mg cm−2 delivers a high areal capacity of 12.9 mA h cm−2, and long-term cycling stability with a slow decay rate of 0.035% per cycle during 1000 cycles at 1C. Additionally, the pouch cell shows foldable flexibility and a stable areal capacity of 5.9 mA h cm−2 at a sulfur loading of 7.1 mg cm−2. The results show that enhancing the polysulfide conversion process kinetics using sulfur vacancies could be an effective approach for obtaining high-performance lithium–sulfur batteries. [ABSTRACT FROM AUTHOR]

In this communication, a simple solar rechargeable battery based on the sodium ion storage mechanism with Fe2(MoO4)3 microspheres as anode materials is proposed for the first time. The battery can be photo-charged under solar irradiation, and discharged reversibly in the dark. Therefore, photon–electron conversion, and energy storage and release based on reversible sodium ion insertion and extraction can be realized in the solar rechargeable battery. [ABSTRACT FROM AUTHOR]

Li-rich layered oxides have been intensively investigated as cathodes for high energy lithium-ion batteries. However, oxygen loss from the lattice during the initial charge and gradual structural transformation during cycling can lead to capacity degradation and potential decay of the cathode materials. In this work, Sn4+ is used to partially substitute Mn4+ to prepare a series of Li(Li0.17Ni0.25Mn0.58−xSnx)O2 (x = 0, 0.01, 0.03, and 0.05) samples through a spray-drying method. Structural characterization reveals that the Sn4+ substituted samples with a suitable amount show low cation mixing, indicating an enhanced ordered layer structure. Moreover, the metal–oxygen (M–O) covalency is gradually decreased with increasing Sn4+ amount. It is shown from the initial charge–discharge curves that Sn4+ substituted samples present a shorter charging potential plateau at 4.5 V (vs. Li/Li+), implying that oxidation of the O2− ion to O2 is suppressed by Sn4+ substitution and leads to a minor structural change. Among the Sn4+ substituted samples, the Li(Li0.17Ni0.25Mn0.55Sn0.03)O2 sample exhibits a higher capacity retention of 86% after 400 cycles at 0.1C rate and 92% after 200 cycles at 1C rate, showing excellent cycle stability and high-rate capability as compared with the as-prepared sample. The electrochemical performance improvement can be attributed to the influences of Sn such as enlarging the Li ion diffusion channel due to the large ionic radius of Sn4+ substitution with respect to Mn4+, a higher bonding energy of Sn–O than Mn–O, and weakening the M–O covalency. All the influences are favorable for stabilization of the host lattice in Li-rich layered oxides. [ABSTRACT FROM AUTHOR]

The performance of the metallic lithium anode is one of the major factors that affect the cycle stability of a lithium–sulfur battery. The protection of the lithium anode is extremely essential, especially for lithium–sulfur full-cells. Here, a porous Al2O3 layer is fabricated on the surface of a metallic lithium anode by using a spin-coating method as protective layer for a lithium–sulfur battery. The porous Al2O3 protective layer acts as a stable interlayer and suppresses the side reactions between soluble lithium polysulfides and lithium anode by direct contact during the charge–discharge process. In addition, the inhomogeneous dissolution–deposition reaction, and the formation of serious cracks on the protected lithium anode are suppressed to a certain extent, which is beneficial to ensure the good and stable electrochemical activity of the lithium anode. Correspondingly, the sulfur cathode with the protected lithium anode exhibits improved electrochemical performance, accompanied simultaneously with relatively homogeneous lithium deposition on the anode surface due to the even distribution of Li ion flux via the Al2O3 protective layer. [ABSTRACT FROM AUTHOR]

A hybrid carbon substrate as a sulfur immobilizer is obtained via simple processes to fabricate cathode materials for lithium–sulfur batteries. The microstructure and morphology of the sulfur/carbon composites are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It is demonstrated that commercial carbon black and multi-walled carbon nanotubes (CNTs) in the hybrid substrate cooperate well with each other in an appropriate mass ratio. In particular, a large sulfur content of 81.7 wt% can be loaded into the hybrid carbon substrate forming the sulfur/carbon composite. When the mass ratio of carbon black and CNTs is 1 : 1, the composite delivers a high initial capacity of 837.3 and 685.9 mA h g−1(composite) at the current densities of 80 and 160 mA g−1(composite) when used as a cathode-active material. The discharge capacity remains at 554.4 mA h g−1(composite) at a current density of 160 mA g−1(composite) after 150 cycles, indicating a low capacity fading of about 0.12% per cycle. Besides, the composite offers a high Coulombic efficiency of about 100%. The significant improvements in the electrochemical performance are associated with the desirable combination of carbon black and CNTs in the hybrid carbon substrate. Therefore, this work proposes a low-cost and effortless approach to prepare sulfur/carbon composites with high performance as cathodes for lithium–sulfur batteries. [ABSTRACT FROM AUTHOR]