硼粉粒径对锂硼合金结构和电化学性能的影响

Effects of particle size of boron on the structure and electrochemical performance of lithium-boron alloys

金属锂具有高比容量、低密度、低电化学电位,是锂二次电池负极的候选材料,但金属锂在循环过程中不可控的锂枝晶生长和剧烈的体积变化易造成巨大的安全隐患。Li-B合金因存在三维多孔纤维状骨架可以降低局部电流密度,缓解锂枝晶的生长并减少体积变化。采用不同粒径的无定形硼粉制备Li-B合金负极,研究硼粉粒径对Li-B合金的结构和电化学性能的影响。研究结果表明:由平均粒径为1.49μm的硼粉制备的锂硼合金的骨架孔隙尺寸最小,锂在沉积/溶解过程中会出现堵塞。由平均粒径为3.12μm的硼粉制备的锂硼合金,具有大小合理、分布均匀的骨架孔隙,有利于锂的沉积、溶解;Li-B合金对称电池具有最低的过电位(0.13 V)和最低的界面电阻,以LiNi_(0.5)Co_(0.2)Mn_(0.3)O_(2)为正极的全电池具有最高的比容量。

Lithium metal has high specific capacity,low density and low electrochemical potential,and a candidate material for the anode of lithium secondary batteries,but the uncontrollable growth of lithium dendrites and the drastic volume change of lithium during cycling lead to huge security risks.The three-dimensional porous fibrous framework of Li-B alloy can reduce the local current density,alleviate the growth of lithium dendrites and reduce the volume change.In this paper,amorphous boron powders with different particle sizes were used to prepare Li-B alloy anodes,and the effect of boron powder particle size on the structure and electrochemical properties of Li-B alloys was studied.The results show that the skeleton pore size of lithium boron alloy prepared from boron powder with average particle diameter of 1.49μm is the smallest,and lithium will be blocked during deposition/dissolution.The lithium boron alloy prepared by boron powder with average particle diameter of 3.12μm has a reasonable size and uniform distribution of skeleton pores,which is conducive to the deposition and dissolution of lithium.In the symmetric battery,it exhibits the lowest overpotential(0.13 V)and the lowest interfacial resistance.In the full battery with LiNi_(0.5)Co_(0.2)Mn_(0.3)O_(2)as the cathode,it has the highest specific capacity.