RESUMEN
Lithium-sulfur (Li-S) batteries are promising candidates for next generation rechargeable batteries because of their high energy density of 2600 W h kg-1. However, the insulating nature of sulfur and Li2S, the "shuttle effect" of lithium polysulfides (LiPSs), and the volumetric change of sulfur electrodes limit the practical application of Li-S batteries. Here, lychee-like TiO2@TiN hollow spheres (LTTHS) have been developed that combine the advantages of high adsorption TiO2 and high conductivity TiN to achieve smooth adsorption/spread/conversion of LiPSs and use them as a sulfur host material in Li-S batteries for the first time. The cathode exhibits an initial specific capacity of 1254 mA h g-1 and a reversible capacity of 533 mA h g-1 after 500 cycles at 0.2C, which corresponds to an average coulombic efficiency up to 99%. The cell with the LTTHS@S cathode achieved an extended lifespan of over 1000 cycles. Such good performance can be assigned to the good adsorption and catalysis of the dual-function TiO2@TiN composite. This work proved that the TiO2@TiN composite can be an attractive matrix for sulfur cathodes.
RESUMEN
Lithium-sulfur batteries are considered the most promising next-generation energy storage devices. However, problems like sluggish reaction kinetics and severe shuttle effect need to be solved before the commercialization of Li-S batteries. Here, we successfully prepared ZnO quantum dot-modified reduced graphene oxide (rGO@ZnO QDs), and first introduced it into Li-S cathodes (rGO@ZnO QDs/S). Due to its merits of a catalysis effect and enhancing the reaction kinetics, low surface impedance, and efficient adsorption of polysulfide, rGO@ZnO QDs/S presented excellent rate capacity with clear discharge plateaus even at a high rate of 4C, and superb cycle performance. An initial discharge capacity of 998.8 mA h g-1 was delivered, of which 73.3% was retained after 400 cycles at a high rate of 1C. This work provides a new concept to introduce quantum dots into lithium-sulfur cathodes to realize better electrochemical performance.
RESUMEN
Hierarchical structured porous NiMn2O4 microspheres assembled with nanorods are synthesized through a simple hydrothermal method followed by calcination in air. As anode materials for lithium ion batteries (LIBs), the NiMn2O4 microspheres exhibit a high specific capacity. The initial discharge capacity is 1126 mA h g-1. After 1000 cycles, the NiMn2O4 demonstrates a reversible capacity of 900 mA h g-1 at a current density of 500 mA g-1. In particular, the porous NiMn2O4 microspheres still could deliver a remarkable discharge capacity of 490 mA h g-1 even at a high current density of 2 A g-1, indicating their potential application in Li-ion batteries. This excellent electrochemical performance is ascribed to the unique hierarchical porous structure which can provide sufficient contact for the transfer of Li+ ion and area for the volume change of the electrolyte leading to enhanced Li+ mobility.
