Cathode Materials with Two-Dimensional Structure

This chapter provides the relationships between structural and electrochemical properties of lamellar compounds the 3d-transition metal oxides currently studied as for their potential use in LiBs. First, we examine briefly three binary layered oxides, M0O3, V2O5, and LiVsOg which were proposed as intercalation compounds since at the end of 1970s. Then, the ternary layered oxides are considered. Starting from the historical and prototype compound LiCo02, which is the dominant positive electrode material employed by all Li-ion cell manufacturers so far, we state the broad family of layered oxides such as LiM Oy and their derivatives the 

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Many of the lithium battery cathode materials have a layered structure, which enables the two-dimensional diffusion of the lithium ion, or a spinel structure, which enables the three-dimensional diffusion. The structures of the cathode materials in the lithium- ion battery are summarized, together with its electrochanical properties and stability of structure, in Table 2.1. 

The LIB cathode materials are transition metal oxides containing lithium, and they are a type of functional ceramics. For such a material to be used as LIB cathode, the Li ions must be able to diffuse freely through the crystal stmcture. The morphology of the crystal structure, being one-, two-, or three-dimensional, determines the number of dimensions in which Li ions are able to move. Cathode materials currently in use or under development are described below in accordance with the following three morphologies. 

Three-dimensional electrode arrays have been fabricated using two very different micromachining methods. One approach, named carbon MEMS or C-MEMS, is based on the pyrolysis of photoresists. The use of photoresist as the precursor material is a key consideration, since photolithography can be used to pattern these materials into appropriate structures. The second approach involves the micromachining of silicon molds that are then filled with electrode material. Construction of both anode and cathode electrode arrays has been demonstrated using these microfabrication methods. 

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