LiNixCoyMn1-x-yO2 Cathode Material Synthesized through Construction of E-pH Diagram and Its Electrochemical Performance

The thermodynamic data of various species in Li-Ni-Co-Mn-H2O system is obtained by thermodynamics calculation, and E-pH diagrams for Li-Ni-Co-Mn-H2O system with activity 1.00 at 25 degrees C. and 200 degrees C were constructed. From E-pH diagrams, it shows that there is no predominant region of the LiNixCoyMn1-x-yO2 composite oxide in pH range of 3 similar to 13 at 25 degrees C. However, the stability region of various species expands towards the low pH and low potential zones as the temperature increases. When pH is between 9.7 similar to 13.0 at 200 degrees C, synthesis of LiNixCoyMn1-x-yO2 via aqueous process is thermodynamically possible, and high temperature is favorable. Experimental results showed that the composite precursor (LNCM) with alpha-NaFeO2 structure was successfully prepared in aqueous solution by using (Ni0.5Co0.2Mn0.3)(OH)(2) as precursor and LiOH center dot H2O as raw material. LiNi0.5Co0.2Mn0.3O2 cathode materials were then obtained by post heat treatment and following tests exhibited excellent cycling performance. These experimental results are in consistent with the information given in E-pH diagram of the Li-Ni-Co-Mn-H2O system, and the as-prepared LiNi0.5Co0.2Mn0.3O2 cathode materials show excellent cycling performance.