There are several factors, which influence the electrochemical properties of LiNi0.5Mn1.5O4. Two of those are the amount of manganese(III) in the cathode material and a electrochemical inactive impurity phases. One important factor of influence for the formation of the manganese(III) content in LiNi0.5Mn1.5O4 and an impurity phase, which often consist of NixO and/or LixNi1-xO, is the oxygen content at the sample while the temperature treatment. [1] We used two different approaches to control the oxygen amount at the sample while the calcination. A chemical and a procedural approach where chosen. For the chemical method precursors with different composition of nitrate and acetate salts were used, which therefore changes the chemical composition of the precursor. Those salts show different gas removal at high temperature and therefore lead to a different environment for the sample while the calcination. For the procedural approach different kinds of calcination environments where used. By using a rotary kiln for example the resulting gas is removed similar for all the samples no matter the precursor used in comparison to a Muffle furnace.
In our presentation we will present, that by changing the precursor chemistry the manganese(III) amount and the amount of impurity phase of the product can be tinkered. We will show, that the products exhibits a very different shape after the first calcination and therefore a different surface area. A different surface area means a different oxygen content at the sample. Resulting from this fact we will indicate the influence on the manganese(III) amount and the impurity phases. To achieve a systematic understanding all the synthesis materials were analyzed by electrochemical measurements, which will focus around capacity, cycle life and performance. The manganese amount will be calculated from the discharge curve, the impurity phase was analyzed by XRD measurements. Furthermore the samples were characterized by SEM, RAMAN to achieve information about the space group and BET to obtain information about the surface area of the samples. Furthermore we will show how to reduce the influence of those shapes by controlling the gas removal over using a rotary kiln. Resulting from this outcome the chemical and procedural approach can improve the electrochemical properties with rather easy ably able methods, which can be scaled into an industrial format.
Acknowledgment
The authors wish to thank for financial support by the BMBF (Bundesministerium für Bildung und Forschung) within the BaMoSa (Batterie – mobil in Sachsen) project.
[1] Pasero, D. Reeves, N. Pralong, V. & West, A. R., J. Electrochem. Soc. 155, A282 (2008).