Invited Presentation: High-Energy Cathode Material for Advanced Lithium-Ion Batteries

A great attention has been made on development of lithium-ion batteries with high energy density and long cycle life for automotive applications such as plug-in hybrid vehicles (PHEVs) and electric vehicles (EV). A successful use in the automotive sectors, where both energy density and safety is of great importance, requires further increase in energy density, cycle life, and safety. Meeting this challenge has centered on finding new cathode materials with high capacity and excellent safety which is the major factor deciding for the real battery applications

One of the promising candidates for such batteries, Li[Ni_0.8Co_0.1Mn_0.1]O₂ (Ni-rich NCM) and Li[Ni_0.8Co_0.15Al_0.05]O₂ (NCA) have been studied extensively for the last decade [1,2]. Though these materials deliver high capacity of 200 mAh g^-1 (4.3 V cutoff voltage), they exhibit very poor thermal characteristics and cycling stability, particularly elevated temperature]. One of the most promising oxides is a core-shell (with gradient) [3] or full concentration gradient lithium nickel-cobalt-manganese oxide [4] composed of a Mn-rich outer surface providing excellent safety and Ni-rich center achieving high capacity. This new approach has made it possible to design and develop materials with different gradient compositions and slopes within a particle.

In this presentation, we report a novel cathode material with two slope full concentration gradients (TSFCG) of Ni, Co, and Mn ions extending throughout each particle to increase average active redox species of Ni concentration and the lower Mn concentration in the particle outer surface. The Ni-rich TSFCG delivers a high capacity of more than 200 mAh g^-1 (4.3 V cutoff voltage) with excellent cycle life and good thermal properties. Furthermore, the electrochemical and thermal properties of the TSFCG were compared with those of NCA and conventional cathode (C.C.).

 References:

1. Kostecki, R. & McLarnon, F.: Local-probe studies of degradation of composite LiNi_0.8Co_0.15Al_0.05O₂ cathodes in high-power lithium-ion cells. Electrochem. Solid State Lett. , 2004, 7, p. A380_A383.
2. Kim, M.-H., Shin, H.-S., Shin, D. & Sun, Y.-K.: Synthesis and electrochemical properties of Li[Ni_0.8Co_0.1Mn_0.1]O₂ and Li[Ni_0.8Co_0.2]O₂ via co-precipitation. J. Power Sources, 2006, 159, p. 1328-1333.
3. Sun, Y.-K. Sun, Myung S.-T., Park B.-C., Prakash J., Belharouak I., Amine K.:  High-energy cathode material for long-life and safe lithium batteries, Nature Mat., 2009, 8 (4), p. 320-324.
4. Sun Y.-K. Sun, Chen Z., Noh H.-J., Lee D.-J., Jung H.-G., Ren Y., Wang S., Yoon C. S., Myung S.-T., Amine K.: Nanostructured high-energy cathode materials for advanced lithium batteries, Nature Mat., 2012, 11(11), p. 942-947.