Porous graphitic carbon loading ultra high sulfur as high-performance cathode of rechargeable lithium-sulfur batteries.

Porous graphitic carbon of high specific surface area of 1416 m(2) g(-1) and high pore volume of 1.11 cm(3) g(-1) is prepared by using commercial CaCO3 nanoparticles as template and sucrose as carbon source followed by 1200 °C high-temperature calcination. Sulfur/porous graphitic carbon composites with ultra high sulfur loading of 88.9 wt % (88.9%S/PC) and lower sulfur loading of 60.8 wt % (60.8%S/PC) are both synthesized by a simple melt-diffusion strategy, and served as cathode of rechargeable lithium-sulfur batteries. In comparison with the 60.8%S/PC, the 88.9%S/PC exhibits higher overall discharge capacity of 649.4 mAh g(-1)(S-C), higher capacity retention of 84.6% and better coulombic efficiency of 97.4% after 50 cycles at a rate of 0.1C, which benefits from its remarkable specific capacity with such a high sulfur loading. Moreover, by using BP2000 to replace the conventional acetylene black conductive agent, the 88.9% S/PC can further improve its overall discharge capacity and high rate property. At a high rate of 4C, it can still deliver an overall discharge capacity of 387.2 mAh g(-1)(S-C). The porous structure, high specific surface area, high pore volume and high electronic conductivity that is originated from increased graphitization of the porous graphitic carbon can provide stable electronic and ionic transfer channel for sulfur/porous graphitic carbon composite with ultra high sulfur loading, and are ascribed to the excellent electrochemical performance of the 88.9%S/PC.

Facile synthesis of hierarchical micro/nanostructured MnO material and its excellent lithium storage property and high performance as anode in a MnO/LiNi0.5Mn1.5O(4-δ) lithium ion battery.

Hierarchical micro/nanostructured MnO material is synthesized from a precursor of MnCO3 with olive shape that is obtained through a facile one-pot hydrothermal procedure. The hierarchical micro/nanostructured MnO is served as anode of lithium ion battery together with a cathode of spinel LiNi0.5Mn1.5O(4-δ) material, which is synthesized also from the precursor of MnCO3 with olive shape through a different calcination process. The structures and compositions of the as-prepared materials are characterized by TGA, XRD, BET, SEM, and TEM. Electrochemical tests of the MnO materials demonstrate that it exhibit excellent lithium storage property. The MnO material in a MnO/Li half cell can deliver a reversible capacity of 782.8 mAh g(-1) after 200 cycles at a rate of 0.13 C, and a stable discharge capacity of 350 mAh g(-1) at a high rate of 2.08 C. Based on the outstanding electrochemical property of the MnO material and the LiNi0.5Mn1.5O(4-δ) as well, the MnO/LiNi0.5Mn1.5O(4-δ) full cell has demonstrated a high discharge specific energy ca. 350 Wh kg(-1) after 30 cycles at 0.1 C with an average high working voltage at 3.5 V and a long cycle stability. It can release a discharge specific energy of 227 Wh kg(-1) after 300 cycles at a higher rate of 0.5 C. Even at a much higher rate of 20 C, the MnO/LiNi0.5Mn1.5O(4-δ) full cell can still deliver a discharge specific energy of 145.5 Wh kg(-1). The excellent lithium storage property of the MnO material and its high performance as anode in the MnO/LiNi0.5Mn1.5O(4-δ) lithium ion battery is mainly attributed to its hierarchical micro/nanostructure, which could buffer the volume change and shorten the diffusion length of Li(+) during the charge/discharge processes.