| Tin-based material for its high specific capacity (990mAh·g-1) is expected to replace the carbon material as a new Li-ion battery electrode material. This paper reviews the development of lithium-ion batteries, focus on the anode electrode material. The SnCo materials were prepared by both ball-milling and chemical reduction and the electrochemical performances of them were studied.The active material, active material & acetylene carbon, active material & acetylene carbon & PVDF and the entire electrode of anode were heat-treated respectively. Compared with the electrode without any heat-treatment, every kind of heat-treatment was beneficial to the electrochemical performance of the electrode. The electrode that entirely was heat-treated had the best performance, whose capacity was 600mAh·g-1 in 1st cycle and matianed above 300mAh·g-1 after 80 cycles. As to Sn-based material, it was a good measure for improving its electrode property to heat-treat the entire electrode.Three kinds of different atomic ratios of SnCo materials (Sn:Co=1:1, 2:1, 4:1) doped different content of carbon were prepared by the method of ball-milling. The samples of SnCo with 5mass% graphite and Sn4Co with 20mass% and 30mass% acetylene black all had bad properties with low capacity and rapid fading. Compared the sample of Sn2Co added 5mass% acetylene black with the sample of Sn2Co added 5mass% graphite, the SEM images showed the particles of the former were smaller and more homogeneous, and the sheet of graphite embedded into the particles of the latter. XRD indicated there was the crystal Sn in the latter, which wasn't found in the former. The former had a better electrochemical performance. The sample of 5mass% acetylene black had a capacity of 400mAh·g-1 after 60 cycles. On the basis of the sample doping 5mass% acetylene black, the electric agent acetylene black was also joined into SnCo in the form of milling, the sample contenting 15.5mass% acetylene black had been made. Its performance had been greatly improved: the initial capacity of Li-extraction was 680mAh·g-1, through 60 cycles the capacity was still 530mAh·g-1. The samples of doping 20mass% and 25mass% acetylene black were made by this means too, but their performances were not good. The performance comparison of three samples in which the amount of acetylene black were respectively 15.5mass%, 20mass%, 25mass% revealed the rule that the more the content of acetylene black, the lower the capacity and the faster the decay.Adopting chemical reduction the material of better properties was synthesized. The initial irreversible loss of capacity was 28%, and the first capacity of Li-extraction reached 822mAh·g-1. After 80 cycles the capacity could keep 630mAh·g-1. Coulomb efficiency basically maintained above 97%. Tin oxides were detected in XRD analysis, ICP test showed the material containing a small amount of boron. These factors such as the dimension of particles, the mass of active material in electrode, the existence of tin oxides, had been excluded. Finally reaction condition was confirmed to respond for the good performance. Reaction condition decided the amount of the amorphous compounds CoB, that affected the overall structure of materials and electrochemical properties. ICP analysis indicated that the pH of the reaction system had a great impact on it. In the alkaline environment of pH 12 the content of boron in the sample was small. Contrarily, in an acidic environment it was relatively more. When the pH of the system was same, the existence of cobalt was greatly beneficial for the creation of boron, especially in an acidic environment. Several other approaches such as mechanical milling, milling of stepwise adding tin, the integration of milling and emulsification were attempted to produce ternary materials SnCoB. However, the performances of materials prepared were bad.In this paper, such structure that tin was dispersed into amorphous compound, can greatly alleviate the expansion caused by the Li-inertion. The Sn-based material of high capacity and good cyclic performance was hopefully obtained in this way. This paper provides a novel approach to improve the Sn-based material. |
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