Controlled Preparation Of Porous Metallic Oxide(Sulfide)Based Anode Materials For Lithium-Ion Batteries

Lithium-ion batteries(LIBs)have been used extensively in portable electronics and will be a' very important part of long-lasting and green rechargeable energy sources.Transition metal oxides/sulfides are regarded as promising anode materials for LIBs because of their higher theoretical capacities compared to commercial graphite(theoretically 372 mAh g-1)and natural abundance.However,due to the huge volume variation and inherent poor electrical conductivity,the poor cycling performance and rate performance limit the pratical application of transition metal oxides/sulfides as the anode materials for LIBs.Therefore,the rational design and facile synthesis are of great importance and necessity to improve the electrochemical performance of the transition metal oxides/sulfide-based anode materials.For reasons given above,we attempted to construct some novel porous composite nanomaterials of metal oxides/sulfide and graphenes in this work by calcining appropriate percursors containing two transition metal ions in controlled atmospheres.Our experiment results demonstrated that the performances of the as-prepared porous composites as anode materials of LIBs were closely associated with their compositions and structures.The present work might open the window for developing next-generation anode materials for high energy/power-density battery applications.The main results and conclusion of our study are listed below:(1)Porous MnZnOx@rGO composites with different compositions(4MnZnOx@rGO,0.4MnZnOx@rGO,0.04MnZnOx@rGO and ZnOx(@rGO)were synthesized by simply calcining the precursor MnZnGO with different Mn/Zn ratios at 500 ? in argon atmosphere,and were measured as anode materials for lithium ion batteries.Among these MnZnOx@rGO composites,the 0.4MnZnOx@rGO presented the best performance,and the discharge specific capacity reached 1368 mAh·g-1 for the first cycle and maintained 812 mAh·9-1 after 100 cycles.Structurally,the 0.4MnZnOx@rGO was actually built with ZnMn2O4 nanoparticles wrapped with a carbon layer uniformly distributed on the rGO nanosheets.The mesoporous structure,the carbon shell coating on the surface of ZnMn2O4,and the rGO support synergistically contributed to the superior performance of the as-synthesized composite anode material.(2)A series of bimetallic sulfides(CoxZnyS,x = 0,2,25,50,75,85,95,and 100;y=100-x)with different Co/Zn ratios were successfully prepared by calcining a mixture of Co/Zn-metallic MOFs and sulfur powder at 600 ? under Ar atmosphere or Ar+H2 atmosphere.The effects of the Co/Zn ratio in Co/Zn-MOF precursors and the calcination atmosphere on the properties of lithium battery were systematically investigated.The results show that the bimetallic sulfides with small amounts of Co2+obtainted via the calcination under Ar+H2 atmosphere exhibited relatively better lithium battery performances.