Studies Of The Layered Li_xMnO₂ As A Cathode Material For Rechargeable Lithium Batteries

The preparation conditions of ion exchange technique adopted by the syntheses of layered LixMnO2 was studied. Under the simple and maneuverable condition that the powders were mixed by the sol-gel method, then ground and heated in air, but not in Ar2 or other inertia ambience and without being pressed to pellets, after heated, the powders were quenched in 0@ homemade ice water, we also synthesized the precursor, sodium bronzes with P2 structure. The O2-type Li2/3MnO2 and Li2/3[Ni1/3Mn2/3]O2 prepared by ion exchange in P2-type Na2/3MnO2 and Na2/3[Ni1/3Mn2/3]O2 exhibited excellent electrochemical properties with a large reversible capacity, a good capacity retention vs. cycle number and a high discharge efficiency. On the basis of analyzing the preparation process and the result for precursors and products, it was found that heating time and refrigeration quomodo were two main factors in the precursors' structure under 800@. The factors that precursors mixed with Li, Co, Ni, etc. influenced on composition, structure and properties of products were studied.The ion exchange quomodo was innovated, and the idea was first brought forward that the ion exchange reaction were occurred after the precursors were pretreated. The ion exchange reaction in molt salt was further studied. After analyzing the preparation conditions and the result for precursors and products, temperature, time and Li/Na ratio were central factors that impacted the products' composition, structure and electrochemical properties if the medium's influence can be neglected.The structure and cycling properties of O2-type products were studied too. The results proved that the material remained layered and did not transform to the spinal structure during cycling when it was cycled in 2.2-4.2V, it occurred irreversible phase transformation only when it further discharged to 1.0V. The granularity, shape and density of the grain were also studied.The adulteration and melioration experiment of the materials prepared by acid-treating method were studied, the results proved that the material treated had an excellent steady property, but less reversible capacity.To some extent, the study was beneficial for developing the simply syntheses technology of layered LixMnO2, understanding the basic theory concerned with the preparation of layered cathode materials, and researching the structure and characteristics of layered LixMnO2.