Electrochemical characterization of lithiated transition metal oxide cathode particles in the absence of carbon, binders and other additives

A novel method is herein described for the electrochemical characterization of lithiated transition metal oxides in powder form as cathode materials f or lithium ion batteries. The procedure involves application of sufficientl y high pressures to a layer of oxide powder evenly dispersed on the surface of a Au foil so as to embed the particles into the soft metal substrate, t hereby avoiding the use of carbon, binders and other additives. Implementat ion of this methodology for battery-grade LiMn2O4, LiCoO2 and LiCo0.15Ni0.8 5O2 particles supplied by various commercial sources yielded electrodes of excellent mechanical integrity displaying close to ideal cyclic voltammetri c behavior in electrolytes of relevance to battery applications. The charge capacity of each of these compounds could be estimated quantitatively by d issolving the array of oxide particles in acid, once the electrochemical ex periments were completed and then determining the amount of metal in the so lutions by ICP-MS analysis. An analysis of voltammetric measurements as a f unction of scan rate yielded values of mean diffusion coefficients for Li i n LiMn2O4 on the order of 5 x 10(-10) cm(2) s(-1). (C) 1999 Elsevier Scienc e Ltd. All rights reserved.