The Preparetion And Lithiation Properties Of SnO₂-based Composite Anode Materials

Owing to relatively high theoretical capacity, low operating potential, natural abundance and bargain price, SnO₂ has been considered as a potential Li- ion anode material. However, two main problems limit the application of SnO₂ anode, one is the low initial coulombic efficiency（IC E） caused by the irreversible Li2 O formed in the initial cycle; the other is the fast pulverization and aggregation of Sn caused by the large volume expansion, which leads to a rapid decay and short cycling life. In order to alleviate or overcome the above problems of SnO₂ anode, SnO₂/Mn and SnO₂/Mn/Graphite composite anode materials were prepared by mechanical milling. We focus preparation parameters on the microstructure and electrochemical performance of the composite anodes, which include the milling time and the amount of Mn and carton Then, SnO₂/Mn/Graphite full cells has assembled with different cathode, we focus on influence factors of full cell capacity. The main conclusions are as follows:Firstly, the SnO₂/Mn composites were prepared by mechanical milling. The results show that the average ICE of SnO₂/Mn composite milled for 20 h, with 30% mass weight ratio of Mn is 72.8%, which is 20.4% higher than theoretical value of pure SnO₂. The microstructure analysis on the SnO₂/Mn composite show that nanosized SnO₂ were uniformly dispersed in the Mn matrix, which facilitates the reversibility of Li2 O. The composite anode show stable cycling performance with a specific capacity 618.8 mAh/g after 500 cycles at a current of 0.2 A/g.Secondly, SnO₂ was milled with Mn and graphite to prepare SnO₂/Mn/Graphite composite anode material. The results show that the average ICE of SnO₂/Mn/Graphite composite anode is 76.9%. This electrode exhibits a high reversible capacity and excellent rate capability. A reversible capacity up to 914mAh/g is maintained at the current of 0.2A/g after 400 cycles, and even when the current is increased to 2A/g, a capacity of 682mAh/g is retained after 1400 cycles. The reversibility and cyclability of this electrode is dramatically enhanced by preserving the nanostructured Sn/Li2 O mixture, which facilitates the reversible conversion reaction.At last, full cells were assembled with SnO₂/Mn/Graphite as the anode and commercial LiMn2O4, LiN iCoMnO₂ and LiCoO₂ as the cathode. The results show the match of capacity between the two electrodes and the test voltage window influenced the performance of full cell by controlling the reaction degree of active material and lithium deposition, and the capacity fading in the full cell main be caused by lithium deposition. SnO₂/Mn/Graphite||LiCoO₂ show the best cycle performance with a reversible capacity of 734mAh/g for anode at the current of 200mA/g after 40 cycles which is 91% of initial charge capacity.