Carbon-templated strategy toward the synthesis of dense and yolk-shell multi-component transition metal oxide cathode microspheres for high-performance Li ion batteries

Development of efficient strategies for the synthesis of multicomponent microspheres applicable to cathodes in lithium ion batteries is in urgent need. This paper presents ‘drop and dry’ method for synthesizing dense and yolk-shell multicomponent transition metal oxide microspheres. The infiltration of ethanol solution containing several metal precursors into highly porous carbon template microspheres through repetitive drop and dry process and subsequent heat treatment under oxygen atmosphere result in dense and yolk-shell microspheres. The first target cathode material is LiMn_1.5Ni_0.5O₄, which operates at high voltage. After infiltration of Li, Mn, and Ni salts into the pores of the carbonaceous microspheres, stepwise heat treatment under low oxygen flow rate yields dense LiMn_1.5Ni_0.5O₄ microspheres exhibiting non-aggregation characteristics and narrow size distribution. In comparison, one-step oxidation of carbon microspheres containing metal salts under high oxygen flow rate results in yolk-shell LiMn_1.5Ni_0.5O₄ microspheres. The dense and yolk-shell microspheres exhibit stable cycle performance and capacities of 113 and 111 mA h g⁻¹ are delivered after 1200 cycles at 10 C rate, respectively. In addition, discharge capacities of 69 and 44 mA h g⁻¹ for yolk-shell and dense microspheres, respectively, are delivered at a high current density of 50 C.