Interstitial space, insertion materials

A typical lithium-ion cell consists of a positive electrode composed of a thin layer of powdered metal oxide (e.g., LiCo02) mounted on aluminum foil and a negative electrode formed from a thin layer of powdered graphite, or certain other carbons, mounted on a copper foil. The two electrodes are separated by a porous plastic film soaked typically in LiPFe dissolved in a mixture of organic solvents such as ethylene carbonate (EC), ethyl methyl carbonate (EMC), or diethyl carbonate (DEC). In the charge/ discharge process, lithium ions are inserted or extracted from the interstitial space between atomic layers within the active materials. 

In the MnOj family, the / -polymorph is the most stable. It has a rutile-type structure and tetragonal symmetry (Fig. lb). The oxygen ions are arranged in a distorted hexagonal close-packed array (in rutile, sometimes referred to as tetragonal close packing [21]). The Interstitial space in the - MnOj structure consists of narrow (1 X 1) channels. Murphy has reported that crystalline y -MnOj can reach a limiting composition of Lig,2 062 [22], which corresponds to a low electrochemical capacity of 62 mAh g . Crystalline y -MnOj electrodes are, therefore, of little interest as insertion electrodes. Studies have shown that — materials... 

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