摘要
应用量子化学电荷自洽离散变分Xα(SCC-DV-Xα)方法,研究了S-Al、S-Co复合掺杂增强尖晶石结构锂锰氧化物稳定性的作用机制.计算结果表明,S-Al复合掺杂锂锰尖晶石和S-Co复合掺杂锂锰尖晶石中的共价键强度均比未掺杂尖晶石LiMn2O4中的强,且与MnO2中的共价键强度相近;S-Al,S-Co复合掺杂尖晶石中Mn的电荷也与MnO2模型Mn6O2628-中十分接近.Mn原子的电荷密度次序是MnO2≈掺硫铝后锰锂尖晶石≈掺硫钴后的锂锰尖晶石<锰锂尖晶石.即LixMn3Co3O20S6n-和LixMn3Al3O20S6n-中Mn的状态与MnO2中的Mn相似.上述结果揭示了S和非Jahn-Teller效应阳离子(Al3+,Co3+)复合掺杂尖晶石结构锂锰氧化物在电化学过程中不会发生Jahn-Teller畸变的内在原因.
The structural stability of S-Al, S-Co co-doped spinel structure lithium manganese oxide was investigated with self-consistent-charge discrete variational (SCC-DV-Xalpha) method of quantum chemistry. The calculated results show that the average covalences of S-Al co-doped spinel [LixMn3Al3O20S6](n-) and S-Co co-doped spinel [LixMn3Co3O20S6](n-) both are stronger than that of undoped spinel [LixMn6O26](n-), and approach to that of MnO2, the charge of Mn in [LixMn3Al3O20S6](n-) also approaches to that in MnO2 model [Mn6O26](28-); the order of the charge density of Mn atom in various model is as fellows: MnO2 approximate to [LixMn3Al3O20S6](n-) approximate to [LixMn3Co3O20S6](n-) < [LixMn6O26](n-). It is said that the state of Mn in [LixMn3Co3O20S6](n-) and [LixMn3Al3O20S6](n-) is similar to that in MnO2. These results reveale the reason that structural stability of S-Al, S-Co co-doped spinel structure lithium manganese oxide was enhanced during electrochemical cycle.
出处
《物理化学学报》
SCIE
CAS
CSCD
北大核心
2004年第3期233-236,F003,共5页
Acta Physico-Chimica Sinica
基金
国家自然科学基金(59972026)~~
