Exploration Of Novel Anode Materials For Lithium Batteries

In this paper, the recent developments on the anode materials of lithium ion battery are reviewed. Based on the disadvantages of the practical anode materials such as low capacity and poor cycle stability, etc., Fe₃O₄ particles with different size synthesized by a low temperature sol method and nano-sized Si powder with conductive adhesive additives are studied as anode materials for lithum ion battery, respectively., in the aim of developing new type of anode materials of high preformace. The microstructures of the synthesized Fe₃O₄ particles were investigated by XRD, SEM and TEM. The electrochemical properties of anode of Fe₃O₄ and nanosized Si powder appened with conductive adhesive are studied by galvanostatic charge-discharge and cyclic voltammetry(CV) methods. The effects of particle size of Fe₃O₄ on the electrochemical properties and the conductive adhesive addition on the electrochemical properties of of the electrode of lithium ion battery are systematically studied.The Fe₃O₄ particles with different size ranging from 50 to 900 nm were successfully prepared by adjusting the content of reactants of FeSO4, KNO₃ and KOH by a low temperature sol method. The study of the electrochemical properties of the electrode prepared from Fe₃O₄ particles of different size shows that the particle size of Fe₃O₄ particle greatly affected the electrochemical properties of anode. The cycle stability is improved by increasing the particle size of Fe3O₄. The results of the study of the positions of the oxidization and reduction peaks of the cyclic voltammetry profiles of the electrod show that the polarization reduced with the increasing of the particle size of Fe₃O₄. Moreover, the study of the effect of the current density varied from 50 to 200mA/g on the capacities of the electrode shows that the current density varied from 50 to 200mA/g has less effect on the capacity of the Fe₃O₄ anode, which indicates that Fe₃O₄ has good rate capacity as anode material.The mechanism of the particle size of Fe₃O₄ on the cycle stability of the anode is discussed in this paper. A SEI film was formed on the surface of the Fe₃O₄ particles during cycling. Fe₃O₄and Li reacted forming a network of LiO₂ and Fe powder of small size. There is larger specific surface area for the smaller Fe₃O₄ particles, therefore there are more amount of LiO₂ and Fe powders desquamated from the surface of the Fe₃O₄ relative to the active material itself. Vice versa for the Fe₃O₄ particles of large size. Thisis the reason why the Fe₃O₄ particle of larger size has better cycle stability than the samller.The study of the cycle stability of the nanoszie Si powder anode appened with conductive adhesive addition shows that as the Si anode with 40wt% of conductive adhesive additives has a charge capacity as high as 3200mAh/g at charge current of 100 mA/g, indicating that the conductive adhesive has electron conductivity and lithum ion conductivity. The study of the cyclic voltammetry of the electrode exhibits that the addition of the conductive adhesive suppressed the reaction of Li and Si during charging process forming Li₇Si₃, reducing the polarization of the anode, therefore increasing the conductivity of the anode.