Polaron inhibited α-trizinc bis-phosphate(v) as low potential polyanionic negative electrode for lithium-ion batteries

This work explores polyanionic phosphate-type α-Zn₃(PO₄)₂ (ZP) as a negative electrode in lithium-ion batteries. It has a high theoretical capacity of 278 mA h g⁻¹. The crystal structure of ZP is elucidated, and Patterson's electron density profiling is performed to understand the possible site of lithiation. To address the polaron-driven electrical insulation common to phosphates, we use superficial carbon coating (ZP/C). Furthermore, the electrochemical analysis of ZP and ZP/C is performed to validate the half-cell performance and Li⁺ kinetics. ZP/C delivers a high capacity of 260 mA h g⁻¹ at 0.1 C. The positive effect of carbon coating is evident from a 100-fold increase in lithium diffusion coefficient from the galvanostatic intermittent titration technique. In addition, temperature-driven capacity performance is analyzed at −10, 25, and 50 °C. Temperature gradient charge-discharge is performed between −10 and −5 °C, where the discharge capacity increases from 70 to 100 mA h g⁻¹ at 1 C rate, extending the application toward low-temperature non-carbonaceous energy storage solutions.