Low Volume-Expansion, Insertion-Type Layered Silicate Hierarchical Structure For Superior Storage Of Li, Na, K

摘要

A hierarchical structure is successfully synthesized by coating polypyrrole (PPy)on the surface of carbon/saponite superlattice (denoted as PPy@C/SAP), andapplied as low volume-expansion insertion-type anode for Li, Na, K storage.The synergistic effect of metal Ni, Fe doping, carbon/silicate superlattice,abundant oxygen vacancies and PPy coating leads to a good electronicconductivity and large current discharging capability. As a Si-based material,PPy@C/SAP has excellent storage capability for Li (659 mAh g~(?1) after1000 cycles at 2 A g~(?1) and 550 mAh g~(?1) after 1000 cycles at 5 A g~(?1)), Na(maximum specific capacity of 533 and 327 mAh g~(?1) after 50 cycles) as well asK (236 mAh g~(?1) after 100 cycles). XPS, XANES, XRD, FTIR, HRTEM, SEM areused to detect the hybrid mechanism (bulk insertion and surface conversion)with a volume expansion as low as 9. Insertion reaction driven by valencestate change of Ni, Fe, Si (Ni~0?Ni~(2+), Fe0?Fe~(3+), Si~(2+)?Si~(4+)) in laminates andconversion reactions between LiOH/Li2CO3 and LiH/Li_2C_2 catalyzed by Ni°contribute to the high performance. In the whole electrochemical process,layered structure is retained while the conversion reactions of LiOH (prodecedby laminates dehydroxylation) and Li2CO3 (electrolyte decomposition)cause the dynamic evolution of solid ectrolyte interphase. This study developsa promising Si-based anode material for lithium ion batteries, sodium ionbatteries and potassium ion batteries, which is significant for designing longcycle life rechargeable batteries.