晶态Li12Si7锂离子电池负极材料的电化学性能研究

通过加热摩尔比为12:7的LiH/Si球磨混合物，避免了Li与Si之间巨大的熔点差异，成功制备了晶态Li₁₂Si₇合金，研究了其电化学性能和储锂机制. 发现Li₁₂Si₇在0.02 ~ 0.6 V的嵌脱锂过程中，只发生晶胞体积的变化，而不产生相变，呈现出明显的固溶储锂机制. 该固溶储锂机制的存在，有效抑制了Si基负极材料嵌脱锂过程中由于相变导致的体积效应，使得晶态Li₁₂Si₇在0.02 ~ 0.6 V电压范围内具有显著改善的电化学性能，其首次库伦效率高达100%，30次循环后的可逆容量保持率约为74%，分别优于相同条件下原始Si电极的55%和37%.

Electrochemical Performance of Crystalline Li12Si7 as Anode Material for Lithium Ion Battery

CrystallineLi₁₂Si₇ is successfully synthesized by heating the mixture of LiH and Si with a molar ratio of 12:7, which avoids the huge difference of the melting points between Li and Si. The electrochemical performance and lithium storage mechanism of the as-prepared Li12Si7 are studied in this work. It is found that only a change in cell volume takes place without a phase change during the lithiation/delithiation ofLi₁₂Si₇ at a voltage range of 0.02 ~ 0.6 V, exhibiting a solid-solution lithium storage mechanism. Such a lithium storage process effectively retards the volume effect caused by the phase change during lithiation/delithiation of Si-based anode. This induces significantly the improved electrochemical properties of crystallineLi₁₂Si₇ while cycling at 0.02 ~ 0.6 V. The first Coulombic efficiency of crystallineLi₁₂Si₇ is determined to be as high as 100%, and the capacity retention is 74% after 30 cycles, which are distinctly higher than those of Si anode (55% and 37%, respectively) under identical conditions.