Regulating solid electrolyte interphases on phosphorus/carbon anodes via localized high-concentration electrolytes for potassium-ion batteries

The resourceful and inexpensive red phosphorus has emerged as a promising anode material of potassium-ion batteries (PIBs) for its large theoretical capacities and low redox potentials in the multi-electron alloying/dealloying reactions, yet chronically suffering from the huge volume expansion/shrinkage with a sluggish reaction kinetics and an unsatisfactory interfacial stability against volatile electrolytes. Herein, we systematically developed a series of localized high-concentration electrolytes (LHCE) through diluting high-concentration ether electrolytes with a non-solvating fluorinated ether to regulate the formation/evolution of solid electrolyte interphases (SEI) on phosphorus/carbon (P/C) anodes for PIBs. Benefitting from the improved mechanical strength and structural stability of a robust/uniform SEI thin layer derived from a composition-optimized LHCE featured with a unique solvation structure and a superior K + migration capability, the P/C anode with noticeable pseudocapacitive behaviors could achieve a large reversible capacity of 760 mA h g −1 at 100 mA g −1 , a remarkable capacity retention rate of 92.6% over 200 cycles at 800 mA g −1 , and an exceptional rate capability of 334 mA h g −1 at 8000 mA g −1 . Critically, a suppressed reduction of ether solvents with a preferential decomposition of potassium salts in anion-derived interfacial reactions on P/C anode for LHCE could enable a rational construction of an outer organic-rich and inner inorganic-dominant SEI thin film with remarkable mechanical strength/flexibility to buffer huge volume variations and abundant K + diffusion channels to accelerate reaction kinetics. Additionally, the highly reversible/durable full PIBs coupling P/C anodes with annealed organic cathodes further verified an excellent practical applicability of LHCE. This encouraging work on electrolytes regulating SEI formation/evolution would advance the development of P/C anodes for high-performance PIBs.