溶胶-凝胶法合成Li_(1-x)Na_xMn_2O_4及其作为水系锂离子电池正极材料的电化学性能

用溶胶凝胶法合成了Na+离子掺杂的Li_(1-x)Na_xMn_2O_4(x=0,0.01,0.03,0.05)。X射线衍射图表明Na+取代Li+进入Li_(1-x)Na_xMn_2O_4晶格中,扫描电镜图看出产物是粒径为100~300 nm的颗粒。恒流充放电测试结果表明,Li_(0.97)Na_(0.03)Mn_2O_4在2C倍率下循环100圈后放电容量保持率比未掺杂的LiMn_2O_4从51.2%提升到84.1%。循环伏安测试表明Na+离子掺杂降低了材料极化且增大了锂离子扩散系数。10C倍率下Li0.97Na0.03Mn2O4仍有79.0 m Ah·g-1的放电容量,高于未掺杂样品的52.1 m Ah·g~(-1)。Na+离子掺杂可以稳定材料结构并提高锂离子扩散系数,从而提高LiMn_2O_4的电化学性能,是一种可行的改性方法。

Aqueous Li-Ion Battery Cathode Material Li1-xNaxMn2O4 Prepared by Sol-gel Method and Its Electrochemical Performance

The Na-doped Li_1-xNa_xMn₂O₄(x=0,0.01,0.03,0.05) was successfully synthesized by a sol-gel method.X-ray diffraction showed Na is successfully doped into LiMn₂O₄ structure.SEM images showed the material is a uniform particle with 100~300 nm particle size.Galvanostatic charge/discharge results show the discharge capacity retention of Li_0.97Na_0.03Mn₂O₄ after 100 cycles at 2C was increased from 51.2% to 84.1% compared with that of undoped LiMn₂O₄.The results of cyclic voltammetry indicate that Na doping reduced the polarization and increased the diffusion coefficient of lithium ions.When the current density is increased to 10C,the doped sample still has a discharge capacity at 79.0 mAh·g^-1,which is higher than that of the undoped sample (52.1 mAh·g^-1).Na doping can stabilize the material structure and improve the diffusion coefficient of lithium ions,thereby improving the electrochemical properties of LiMn₂O₄,is a viable modification method.