Synthesis and Stoichiometric Analysis of a Li-Ion Battery Cathode Material

Abstract

IntroductionGenerally, stoichiometry deals with the quantitative relationship of reactants and products in a chemical reaction.Strictly speaking in areas of materials science, solid-state physics and chemistry, stoichiometric compounds are compounds that have simple ratios to each other, that is, A x B y , where A, B = chemical element and x,y = natural numbers.There is no limit to the number of elements in the molecule.Scientists nowadays modify materials such that their ratios are no longer simple ratios to each other but fractions, for example, Li 0.1 Mg 0.9 O, Li 1.1 Mn 2 O 4 , LiMn 1.7 Fe 0.3 O 2 , Al 1.9 Cr 0.1 O 3 , and countless others.Strictly speaking, these compounds are called non-stoichiometric compounds.There are various reasons for obtaining non-stoichiometric compounds.It is found that processes such as substitution or doping will change, modify or enhance a material's physical and chemical behaviour.Scientists will then have a way to design materials to suit their applications.This can be seen in the well known semi-conductor, Si, whereby doping it with elements of different oxidation states can produce either a p-type or n-type silicon.This technology is very important because nearly all electrical devices are silicon based.The most common cathode materials used in commercial Li-ion batteries is LiCoO 2 (Amatucci et al. 1996; Antolin et al. 2004;Ding et al. 2005).This is because LiCoO 2 gives high energy density as well as good cycling behaviour.However, in terms of economy and availability of elements, Co is considered expensive, not so abundant (Tanaka et al. 2001) and also considered a toxic heavy metal (Shin et al. 2004).Therefore, modification of the material or a complete change of material is warranted in order to have a sustainable technology.There are other reasons for modifying the stoichiometry of cathode materials.It is found that substitution and doping of cathode materials improve the materials' electrochemical behaviour in terms of specific capacity and energy density (Li et al. 2002;Park et al. 2001;Veluchamy et al. 2001).Secondly, it may stabilize the material and improve cycling performance (Fey et al. 2003).Thirdly, it may lower the cost of production by reducing the usage of certain expensive metals such as cobalt and utilizing less expensive metals such as www.intechopen.comStoichiometry and Materials Science -When Numbers Matter 248 Mn or Fe.Last but not least, it may reduce toxicity of the materials and contribute towards a healthier and safer living environment. How to referenceIn order to correctly reference this scholarly work, feel free to copy and paste the following: