Understanding the Configurational Entropy Evolution in Metal-Phosphorus Solid Solution for Highly Reversible Li-Ion Batteries.

Abstract

The high-entropy materials (HEM) have attracted increasing attention in catalysis and energy storage due to their large configurational entropy and multiunique properties. However, it is failed in alloying-type anode due to their Li-inactive transition-metal compositions. Herein, inspired by high-entropy concept, the Li-active elements instead of transition-metal ones are introduced for metal-phosphorus synthesis. Interestingly, a new Znx Gey Cuz Siw P2 solid solution is successfully synthesized as proof of concept, which is first verified to cubic system in F-43m. More specially, such Znx Gey Cuz Siw P2 possesses wide-range tunable region from 9911 to 4466, in which the Zn0.5 Ge0.5 Cu0.5 Si0.5 P2 accounts for the highest configurational entropy. When served as anode, Znx Gey Cuz Siw P2 delivers large capacity (>1500 mAh g-1 ) and suitable plateau (≈0.5V) for energy storage, breaking the conventional view that HEM is helpless for alloying anode due to its transition-metal compositions. Among them, the Zn0.5 Ge0.5 Cu0.5 Si0.5 P2 exhibits the highest initial coulombic efficiency (ICE) (93%), Li-diffusivity (1.11×10-10 ), lowest volume-expansion (34.5%), and best rate performances (551 mAh g-1 at 6400mA g-1 ) owing to its largest configurational entropy. Possible mechanism reveals the high entropy stabilization enables good accommodation of volume change and fast electronic transportation, thus supporting superior cyclability and rate performances. This large configurational entropy strategy in metal-phosphorus solid solution may open new avenues to develop other high-entropy materials for advanced energy storage.