Cr^(3+)掺杂LiSn_2(PO_4)_3负极材料的电化学性能研究

Electrochemical Property of Cr^(3+) Doped LiSn_2(PO_4)_3 Anode Material

利用Cr^(3+)离子对LiSn_2(PO_4)_3化合物中的Sn^(4+)进行掺杂。对所制备的材料Li1+xCrxSn2-x(PO4)3进行X射线衍射(XRD)测试,结果表明,在x=0.1～0.3时可得到单一的α-LiSn_2(PO_4)_3相,掺杂浓度进一步增加则会导致少量SnO_2第二相的析出。尽管引入Cr不能抑制LiSn_2(PO_4)_3在首次放电过程中分解,但x=0.3的样品电化学性能得到显著改善。电池在100和800 mA/g电流密度下25次充放电循环后放电容量分别为403.1和241.9 mAh/g,并具有较好的循环性能和倍率性能。导致上述结果的主要原因是Li_3PO_4和Cr复合基体的空间效应,有效避免了Sn颗粒在充放电循环中的团聚,改善了电化学反应环境,从而提高了Sn颗粒的利用效率。

Sn^4+ in the LiSn2(PO4)3 compound was doped with Cr^3+ ion. Single phase of α-LiSn2(PO4)3 can be obtained with the Cr^3+ contents x=0.1?0.3 for the as-prepared Li1+xCrxSn2?x(PO4)3 samples, which were confirmed by X-ray diffraction (XRD) measurement. Further augment of the Cr^3+ content led to the precipitation of a little secondary phase such as SnO2. Although the introduction of Cr could not prevent the LiSn2(PO4)3 from decomposition during initial discharging, the sample with Cr^3+ content of 0.3 showed remarkably enhanced electrochemical performances. Specific discharging capacities of 403.1 and 241.9 mAh/g could be delivered at current densities of 100 and 800 mA/g after 25 cycles, respectively. Improvement in electrochemical performance could be attributed to the steric effect of complex matrix composed of Li3PO4 and Cr, which was favorable for preventing Sn particles from aggregation during subsequent charge/discharge cycles, Leading to promote utilization efficiency of the precipitated Sn.