The Lithium Titanate Anode Materials With Graphene-like Doped And Coated

As a kind of embedded materials with zero-strain, Li4Ti5O12 anode materials are attracting lots of interest and publicity because of its excellent cycle performance, longer cycle life, lower voltage platform and stable structure. However, the electrical conductivity of Li4Ti5O12 is only 10-9 S/cm, and the poor conductivity restricts the capacity of charge/discharge at high rate, further limiting its application in the field of lithium-ion batteries.The preparation of lithium titanate precursor materials by solid state reaction method, and liquid acrylonitrile oligomer(LPAN) modified by the carbon source, through the LPAN and the precursors were mixed after sintering, the preparation of a new type of graphene coated lithium titanate anode material. The main research contents and results are listed as follows:In the preparation of graphene coated Li4Ti5O12 anode materials, the error ratio of raw materials was reduced and the efficiency of reaction was improved by using the method of premixed and crushing. Compared with conventional ball milling method, the initial charge/discharge capacity of the materials prepared by this method at 0.1C rate reached as much as 171 m Ah/g.Though the content of LPAN had little influence on crystal type of Li4Ti5O12, the cycle stability of materials were improved. When the percentage of LPAN content was 10%, the electrochemical performance of graphene coated Li4Ti5O12 anode materials was best. However, the electrochemical cycle performance under high rate is not good if the lithium carbonate negative material is only coated by graphene. For instance, the discharge specific capacity is only 67.8m Ah/g at 10 C magnification. The second discharge specific capacity of the composite material added 1% acetylene black is up to 127.4 m Ah/g at 10 C magnification, 118.1m Ah/g after 200 circulations and still 94.8 m Ah/g left after 2000 circulations.The main reason of specific capacity attenuation of Li4Ti5O12 at high discharge rate was discussed. The binder of PVDF couldn’t adhere on the surface of electrode and aluminum foil, which attributed to the presence of the carbon layer and the acetylene black. Under the high rate circulation, conductive materials gradually separated, making the conductivity of electrode material decrease and the specific capacity lose.