Microfluidic high-throughput optimization enables scalable synthesis of high-entropy fluorophosphate cathode

Abstract Large-scale synthesis of high-entropy fluorophosphate cathode for high-rate sodium-ion batteries remains a huge challenge due to time-consuming conditional optimization and poor phase purity. Herein, for the first time, we overcome the bottlenecks of large-scale synthesis of high-entropy Na3V1.9M0.1(PO4)2F3 (HE-NVPF) cathode libraries by microfluidic high-throughput optimization (MHO) strategy. Due to precise regulation and in-situ monitoring of nucleation-growth kinetics, the microfluidic in-situ Raman spectrometer achieves high iteration efficiency of conditional optimization with 400 times increase over traditional strategies. Consequently, kilogram-scale HE-NVPF with high phase purity is rapidly synthesized within 2 hours, which delivers stable multielectron transfer, superior Na+ diffusion kinetics and negligible volume expansion/contraction, exhibiting reversible phase transition and excellent structural ruggedness. As a result, the representative Na3V1.9(Ca, Mg, Zr, Mn, Cr)0.1(PO4)2F3 cathode presents record-breaking rate capacity (108.6 mAh g−1 at 50 C), large energy density (371.9 Wh kg−1) and good cycling stability. This MHO strategy can be extended to synthesize other high-entropy Na3V1.9M0.1(PO4)2F3, such as M= (Mg, Zr, Co, Mn, Cr), (Zr, Ca, Fe, Mn, Cr), (Mg, Ca, Ni, Mn, Cr), (Zr, Cu, Mg, Mn, Cr) and (Ga, Zr, Ca, Mn, Cr). Our work provides a novel insight into machine intelligent synthesis of high-entropy materials and facilitates their industrialized process.