Zn(Cu)Si_2+xP₃ Solid Solution Anodes for High-Performance Li-Ion Batteries with Tunable Working Potentials

Si-based anodes with a stiff diamond structure usually suffer from sluggish lithiation/delithiation reaction due to low Li-ion and electronic conductivity. Here, a novel ternary compound ZnSi₂P₃ with a cation-disordered sphalerite structure, prepared by a facile mechanochemical method, is reported, demonstrating faster Li-ion and electron transport and greater tolerance to volume change during cycling than the existing Si-based anodes. A composite electrode consisting of ZnSi₂P₃ and carbon achieves a high initial Coulombic efficiency (92%) and excellent rate capability (950 mAh g⁻¹ at 10 A g⁻¹) while maintaining superior cycling stability (1955 mAh g⁻¹ after 500 cycles at 300 mA g⁻¹), surpassing the performance of most Si- and P-based anodes ever reported. The remarkable electrochemical performance is attributed to the sphalerite structure that allows fast ion and electron transport and the reversible Li-storage mechanism involving intercalation and conversion reactions. Moreover, the cation-disordered sphalerite structure is flexible to ionic substitutions, allowing extension to a family of Zn(Cu)Si_2+xP₃ solid solution anodes (x = 0, 2, 5, 10) with large capacity, high initial Coulombic efficiency, and tunable working potentials, representing attractive anode candidates for next-generation, high-performance, and low-cost Li-ion batteries. © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.