Scalable Synthesis of Microsized, Nanocrystalline Zn Fe O-C Secondary Particles and Their Use in Zn Fe O-C/LiNi Mn O Lithium-Ion Full Cells.

Conversion/alloying materials (CAMs) are a potential alternative to graphite as Li-ion anodes, especially for high-power performance. The so far most investigated CAM is carbon-coated Zn Fe O, which provides very high specific capacity of more than 900 mAh g and good rate capability. Especially for the latter the optimal particle size is in the nanometer regime. However, this leads to limited electrode packing densities and safety issues in large-scale handling and processing. Herein, a new synthesis route including three spray-drying steps that results in the formation of microsized, spherical secondary particles is reported. The resulting particles with sizes of 10-15 μm are composed of carbon-coated Zn Fe O nanocrystals with an average diameter of approximately 30-40 nm. The carbon coating ensures fast electron transport in the secondary particles and, thus, high rate capability of the resulting electrodes. Coupling partially prelithiated, carbon-coated Zn Fe O anodes with LiNi Mn O cathodes results in cobalt-free Li-ion cells delivering a specific energy of up to 284 Wh kg (at 1 C rate) and power of 1105 W kg (at 3 C) with remarkable energy efficiency (>93 % at 1 C and 91.8 % at 3 C).