Layered Mixed Transition Metal Oxide Cathodes with Reduced Cobalt Content for Lithium Ion Batteries

The structural and physical properties of the low cobalt material, LiNi 0.45 Mn 0.45 Co 0.1 O 2, have been investigated. Nearly stoichiometric LiNi 0.45 Mn 0.45 Co 0.1 O 2 with the optimal electrochemical performance was produced at 800 °C by coprecipitation method. A higher synthesis temperature leads to a higher crystallinity and larger particles not influencing the Ni/Li disorder. Nonstoichiometric Li 1+ z (Ni 0.45 Mn 0.45 Co 0.1 ) 1− z O 2, 0.8 ≤ 1 + z ≤ 1.2, were then studied; it was found that the interslab Ni content increases as the lithium content decreases. However, the lithium content in the metal layer decreases simultaneously minimizing the formation of tetrahedral lithium upon charging. As a result, the Li-deficient Li 0.9 (Ni 0.45 Mn 0.45 Co 0.1 ) 1.1 O 2 has the best electrochemical capacity (190 mAh/g between 2.5 and 4.6 V at 0.5 mA/cm 2 ) and cycleability. The electrochemical performance is compared to that of other well-studied Li(Ni y Mn y Co 1−2 y )O 2 materials with y = 1/3, 0.4, 0.425, and 0.5. The magnetism of Li 1+ z (Ni 0.45 Mn 0.45 Co 0.1 ) 1− z O 2 studied in conjunction with the structure is dominated by the ordering of interlayer and intralayer ferrimagnetic clusters. The interlayer clusters nucleate at interslab Ni 2+ ions and their size increases with the Ni/Li disorder, while the intralayer clusters size increases in materials with larger particle size and smaller amount nonmagnetic ions in the transition metal layers. This model allows using magnetism to estimate the character of the transition metal ordering.