Scalable Synthesis of Microsized, Nanocrystalline Zn 0.9 Fe 0.1 O‐C Secondary Particles and Their Use in Zn 0.9 Fe 0.1 O‐C/LiNi 0.5 Mn 1.5 O 4 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$_{0.9}$Fe$_{0.1}$O, which provides very high specific capacity of more than 900 mAh g$^{-1}$ 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$_{0.9}$Fe$_{0.1}$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$_{0.9}$Fe$_{0.1}$O anodes with LiNi$_{0.5}$Mn$_{1.5}$O$_{4}$ cathodes results in cobalt‐free Li‐ion cells delivering a specific energy of up to 284 Wh kg$^{-1}$ (at 1 C rate) and power of 1105 W kg−1 (at 3 C) with remarkable energy efficiency (>93 % at 1 C and 91.8 % at 3 C).