Synthesis and characterization of high-energy, high-power spinel-layered composite cathode materials for lithium-ion batteries

Spinel-layered composites, where a high-voltage spinel is incorporated in a layered lithium-rich (Li-rich) cathode material with a nominal composition x{0.6Li2MnO3 · 0.4[LiCo0.333Mn0.333Ni0.333]O2} · (1 - x) Li[Ni0.5Mn1.5]O4 (x = 0, 0.3, 0.5, 0.7, 1) are synthesized via a hydroxide assisted coprecipitation route to generate high-energy, high-power cathode materials for Li-ion batteries. X-ray diffraction patterns and the cyclic voltammetry investigations confirm the presence of both the parent components in the composites. The electrochemical investigations performed within a wide potential window show an increased structural stability of the spinel component when incorporated into the composite environment. All the composite materials exhibit initial discharge capacities >200 mAh g-1. The compositions with x = 0.5 and 0.7 show excellent cycling stability among the investigated materials. Moreover, the first cycle Coulombic efficiency achieve a dramatic improvement with the incorporation of the spinel component. More notably, the composite materials with increased spinel component exhibit superior rate capability compared with the parent Li-rich material especially together with the highest capacity retention for x = 0.5 composition, making this as the optimal high-energy high-power material. The mechanisms involved in the symbiotic relationship of the spinel and layered Li-rich components in the above composites are discussed. The electrochemical performance of spinel-layered composite cathode materials is investigated, revealing that careful tailoring of the component ratio can produce an optimum material with high energy and high power. The composition with x = 0.5 exhibits the highest capacity retention (C-rate C/25) after 50 cycles and a high-rate capability.