Li(Al_xCo_(1-x))O_2晶体中Co^(3+)电子态的变化及对结构演化的影响

Transformation of electronic state of Co^( 3+) and its influence on the structural development in Li(Al_xCo_(1-x))O_2

研究了应用于锂二次电池正极的新型高能量密度存贮材料Li(AlxCo1 -x)O2 (x =0 1— 0 5 )的磁性 .发现Al3+ 的掺杂可导致Co3+ 中d电子自旋态发生变化 ,即有部分d电子进入高自旋态 .伴随Co3+ 中电子状态的改变 ,材料结构演化也发生了相应变化 ,表现为c a比增大明显减缓 ,较好地解释了材料结构对Vegard定律的正偏离 .这对材料的微观结构与性能设计具有重要意义 .

In this paper we have studied the magnetism of a new cathode material with a high energy density, Li(AlxCo1 - x)O-2 (x = 0.1-0.5), which is used in rechargeable lithium batteries. We found that doping Al can change the spin state of d electron in Co3+, leading to the emergence of high spin d electrons. Accompanied with this, there are also some changes of the structure development which is indicated by the obviously decreasing rate of the increasing value of c/a. This explains the positive deviation of the structure from the Vegard law. This is very important to the design of the microstructure and properties of materials.