Lithium isotope effects accompanying oxidation reactions in lithium ion secondary batteries

在锂离子从钴酸锂（LiCoO2）阴极释放到碳酸乙烯基有机电解质溶液的电化学过程中，发现较重的同位素7Li优先转移到电解质溶液中。与此相反，当电解质溶液中不含锂离子时，没有观察到锂同位素效应。结果表明，电解质溶液的种类控制着阴极与电解质溶液之间锂同位素交换平衡的实现。当使用锂锰氧化物（LiMn2O4）作为正极材料时，无论哪种电解质溶液，锂的较轻同位素6Li都优先释放到电解质相。LiCoO2和LiMn2O4正极在锂同位素效应上的巨大差异似乎主要归因于两种正极材料的结构差异。

In the electrochemical lithium release from a lithium cobalt oxide (LiCoO2) cathode to ethylene carbonate-based organic electrolyte solution containing lithium ions, it was observed that the heavier isotope, 7Li, was preferentially transferred to the electrolyte solution. Contrary to this, no lithium isotope effects were observed when the electrolyte solution contained no lithium ions. It was induced that the kind of electrolyte solution controlled the attainment of the lithium isotope exchange equilibrium between the cathode and the electrolyte solution.When lithium manganese oxide (LiMn2O4) was used as the cathode material, the lighter isotope of lithium, 6Li, was preferentially released to the electrolyte phase, irrespective of the kind of electrolyte solution. The great contrast in lithium isotope effects between LiCoO2 and LiMn2O4 cathodes seemed mostly ascribable to the structural difference between the two cathode materials.