image: This figure illustrates the key contributions of this work: elucidating the synthesis mechanisms of high-entropy cathode materials, accelerating high-throughput screening iteration rates, achieving kilogram-scale production, and delivering exceptional rate performance.
Credit: ©Science China Press
The core objective of material chemical engineering is to leverage chemical engineering theories and methodologies to guide material preparation and processing, thereby developing new unit technologies and theories based on advanced materials. Within this field, high-entropy sodium vanadium fluorophosphates (HE-NVPF) cathode materials are recognized as strategic assets for large-scale energy storage in sodium-ion batteries (SIBs) due to their remarkable electrochemical activity. However, the large-scale synthesis of these materials with high phase purity remains a significant bottleneck challenge. Traditional batch reactors suffer from low iteration efficiency in optimizing reaction conditions, leading to poor phase purity and inferior rate performance—obstacles that have hindered the practical application of HE-NVPF cathode materials in grid-scale energy storage.
To address these challenges, Professor Jianhong Xu from the Department of Chemical Engineering at Tsinghua University, in collaboration with Professor Xingjiang Wu from the School of Chemical Engineering and Technology at Hebei University of Technology, has proposed a high-throughput optimization strategy to mass-produce HE-NVPF cathode materials through microfluidic technology. The team created a specialized "lab-on-a-chip" device equipped with real-time monitoring (a micro-Raman spectrometer) to watch exactly how cathode particles form and grow at a microscopic level. This innovative method allows researchers to find the perfect condition for high-performance materials 400 times faster than traditional laboratory methods.
Guided by these high-throughput theoretical insights, the researchers developed a microfluidic spray drying technology, achieving the rapid, kilogram-scale synthesis of high- phase-purity HE-NVPF cathode materials. The study proved that this technology is a universal toolkit—it works successfully for a wide variety of complex material recipes, paving the way for more efficient and scalable energy storage solutions.
High phase purity ensures that these high-entropy materials possess stable multi-electron transfer capabilities, superior sodium diffusion kinetics, and robust structural integrity. This allows for reversible phase transitions and negligible volume expansion or contraction during charge and discharge cycles. For example, the team’s signature material can charge and discharge at ultra-fast speeds (50C) while maintaining high energy capacity (108.6 mAh/g) and high energy density (371.9 Wh/kg). Even after 500 cycles of high current rate (1C), it still retains 86% of its original capacity. Notably, this performance significantly outperforms cathode materials prepared via traditional batch methods, such as transition metal oxides, polyanionic compounds, and Prussian blue analogs.
“This research provides a transformative theoretical framework and a powerful technical toolkit for the design, rapid screening, and scalable synthesis of high-entropy fluorophosphates and other high-entropy energy materials.” Xu said.
Professor Xu Jianhong (Tsinghua University) and Professor Wu Xingjiang (Hebei University of Technology) serve as the corresponding authors. The lead authors are PhD students Tian Zhicheng and Zhou Yuanzheng from Tsinghua University’s Department of Chemical Engineering.