In Situ X-Ray Diffraction Studies of Cathode Materials in Lithium Batteries

摘要

There is an increasing interest in lithiated transition metal oxides because of their use as cathodes in lithium batteries. LiCoO(sub 2), LiNiO(sub 2) and LiMn(sub 2)O(sub 4) are the three most widely used and studied materials, At present, although it is relative expensive and toxic, LiCoO(sub 2) is the material of choice in commercial lithium ion batteries because of its ease of manufacture, better thermal stability and cycle life. However, the potential use of lithium ion batteries with larger capacity for power tools and electric vehicles in the future will demand new cathode materials with higher energy density, lower cost and better thermal stability. LiNiO(sub 2) is isostructural with LiCoO(sub 2). It offers lower cost and high energy density than LiCoO(sub 2). However, it has much poorer thermal stability than LiCoO(sub 2), in the charged (delithiated) state. Co, Al, and other elements have been used to partially replace Ni in LiNiO(sub 2) system in order to increase the thermal stability. LiMn(sub 2)O(sub 4) has the highest thermal stability and lowest cost and toxicity. However, the low energy density and poor cycle life at elevated temperature are the major obstacles for this material. In order to develop safer, cheaper, and better performance cathode materials, the in-depth understanding of the relationships between the thermal stability and structure, performance and structure are very important. The performance here includes energy density and cycle life of the cathode materials. X-ray diffraction (XRD) is one of the most powerful tools to study these relationships.