Sieving carbons promise practical anodes with extensible low-potential plateaus for sodium batteries

Abstract

Non-graphitic carbons are promising anode candidates for sodium-ion batteries, while their variable and complicated microstructure severely limits the rational design of high-energy carbon anodes that could accelerate the commercialization of sodium-ion batteries, as is the case for graphite in lithium-ion batteries. Here, we propose sieving carbons, featuring highly tunable nanopores with tightened pore entrances, as high-energy anodes with extensible and reversible low-potential plateaus (<0.1 V). It is shown that the tightened pore entrance blocks the formation of the solid electrolyte interphase inside the nanopores and enables sodium clustering to produce the plateau. Theoretical and spectroscopic studies also show that creating a larger area of sodiophilic pore surface leads to an almost linearly increased number of sodium clusters, and controlling the pore body diameter guarantees the reversibility of sodium cluster formation, producing a sieving carbon anode with a record-high plateau capacity of 400 mAh g-1. More excitingly, this approach to preparing sieving carbons has the potential to be scalable for modifying different commercial porous carbons.