【摘要】 用高精度非原位XRD结合Rietveld结构精修对固相法制备的正交层状LiMnO2(简写为o-LiMnO2)在电化学循环过程中的相变进行了研究。结果表明:首次循环就出现相变,循环5次后o-LiMnO2相变完全;产物中除了有类尖晶石型锰酸锂(Li0.86Mn0.14)(Mn0.92Li0.08)2O4(Fd3m)外,还证实了文献的理论计算和晶体学推测出的岩盐型锰酸锂(Li,Mn)O2(Fm3m)的存在;并定量计算了两物相的相含量。证实两物相均参与了电化学循环,其中类尖晶石型锰酸锂对电化学容量的变化起主要作用;岩盐型锰酸锂在电化学循环过程中逐渐向类尖晶石型锰酸锂转变,使电极的放电容量不断增加,这种转变停止时,放电容量达到最大,活化过程结束。更多还原

【Abstract】 Layered Orthorhombic LiMnO2(o-LiMnO2) was synthesized via a solid-state reaction. The phase transformation of the material during electrochemical process was investigated using ex-situ high-resolution X-ray diffraction and Rietveld refinement. The results reveal that partial phase transition has been appeared on o-LiMnO2 cathode during the first cycling. After five cycles, o-LiMnO2 has been completely transformed to other products. Two phases as suggested by computational methods(density functional theory) and crystallography in literatures,i.e. spinel-like(Li0.86Mn0.14)(Mn0.92Li0.08)2O4(Fd3m), and rock-salt phase(Li,Mn)O2(Fm3m), have been confirmed to be present in the products. Quantitative analysis was carried out on the abundances of the above two phases. Both of the two phases are proved to be involed in the electrochemical process, and the contribution of discharge capacity of the spinel phase to the process is more than that of the rock-salt one. The rock-salt lithium manganese gradually transforms to spinel one during electrochemical cycling. With the increase of the content of the latter, the discharge capacity of the cathode increases. After the phase transition ceases, the cathode reaches the maximum discharge capacity, and the process of capacity activation ends.更多还原