正交Li1-xMnO2(0≤x≤0.95)首次充电过程中物相及结构的演变

用高精度非原位XRD结合Rietveld精修对正交Li1-xMnO2(简写为o-Li1-xMnO2,0≤x≤0.95)在首次充电(电化学脱锂)过程中物相及结构的演变进行了研究。结果表明,o-LiMnO2电极的电压升高速率与其结构的变化有关;随着电化学脱锂o-LiMnO2发生一系列相变。证实了文献的理论计算和由晶体学推测出的相变过程,即相变产物中先后出现岩盐型锰酸锂和类尖晶石型锰酸锂。相变结束后,产物中只有岩盐型和类尖晶石锰酸锂2种物相。随着充电的进行,都有Li+从岩盐型和类尖晶石锰酸锂晶格中脱出,二者晶胞参数逐渐变小,微结构也不断变化。

Evolutions of Phase and Microstructure of Orthorhombic Li1-xMnO2(0≤x≤0.95)during the First Charge Process

Phase transformation of layered orthorhombic Li1-xMnO2(o-Li1-xMnO2,0≤x≤0.95) during the first charging process(lithium ion deintercalation in electrochemical system) was investigated using ex-situ high-resolution X-ray diffraction and Rietveld refinement.The results reveal that the increasing speed of the o-LiMnO2 cathode’s voltages is related to the change of its microstructure.And a succession of phase transformation of the o-LiMnO2 occurs in the first lithium deintercalation process.Rock-salt typed lithium manganese oxides emerge followed by the appearance of the spinel-like typed,which confirms the phase transition process from theoretical computation and crystallography conjecture in literatures.Only the above-stated type lithium manganese oxides(originated from o-LiMnO2) exist in the final product.Lithium ions extract from lattices of the rock-salt typed and the spinel-like typed lithium manganese oxides;both the lattice parameters become smaller and their microstructures change with the charge proceeding.