Polyanion dominating Li-conductive framework to improve kinetics for lithium storage in iron oxalate

A pioneering phosphate-intercalation strategy is introduced to improve kinetics for lithium storage. • The Fe–O–P framework that actively modulates lithium-ion transport within the iron oxalate lattice. • The optimized anode achieves an exceptional capacity of 1643 mAh g −1 after 300 cycles at 0.5 A g −1 . Iron oxalate has recently attracted considerable interest as a promising conversion-type anode for rechargeable batteries owing to its intrinsically high theoretical capacity. However, its practical application is severely limited by sluggish reaction kinetics, resulting in poor rate performance. In this work, polyanionic phosphate species are introduced as pre-intercalated guest ions to construct a Fe–O–P framework that actively modulates lithium-ion transport within the iron oxalate lattice. Systematic control of the phosphate-to-oxalate substitution ratio effectively tunes the lattice dynamics of FeC 2 O 4 , thereby enhancing the lithium-storage kinetics of the material. Combined experimental characterization and theoretical analysis reveal that phosphate intercalation not only accelerates electron transfer but also enlarges the interlayer spacing that accelerate lithium-ion diffusion. Consequently, the phosphate-intercalated iron oxalate delivers an ultrahigh reversible capacity of 1643 mAh g −1 after 300 cycles at 0.5 A g −1 and maintains a rate capacity of 740 mAh g −1 at 5 A g −1 . This work demonstrates the essential role of the pre-intercalated polyanion on improve kinetics for lithium storage in iron oxalate and provides a rational design strategy for high-performance conversion-type anodes with intrinsically fast lithium-ion transport. Pre-intercalated polyanionic phosphate is introduced into iron oxalate to regulate intrinsic lattice dynamics and accelerate bulk lithium-ion transport. Download: Download high-res image (264KB) Download: Download full-size image