Carbonaceous catalyst boosting conversion kinetics of Na2S in Na-ion batteries

Abstract

Conversion-type metal sulfide anode with high theoretical capacity has received increasing attention in Na-ion batteries (SIBs), but the irreversible conversion of Na₂S intermediate in charging process usually engenders low rate capability and poor cycling stability. Herein, guided by DFT calculation, a new-type carbonaceous graphitic carbon nitride (g-CN) catalyst is first reported to boost conversion kinetics of Na₂S intermediate to pristine MoS₂ in SIBs. Notably, the large chemisorbed energy, high selectivity and low catalytic energy barrier of g-CN catalyst can ensure its affluent charge transfers to Na₂S intermediate, which chemically anchor and decompose Na₂S intermediate for catalyzing its reversible conversion. Moreover, the microfluidic strategy is developed to enhance the mass diffusion of g-CN catalyst precursors into MoS₂ skeleton for facilitating their subsequently covalent bonding process. The covalent bonding of g-CN catalyst on 1T-MoS₂ (1T-MoS₂/g-CN) superlattice with strong interfacial interaction via C-Mo bond can greatly promote Na⁺-storage kinetics of MoS₂ in discharging process and reversible conversion reaction of Na₂S intermediate to pristine MoS₂ in following charging process, which is further evidenced by DFT calculation and in-situ characterizations. Consequently, the 1T-MoS₂/g-CN superlattice reveals superb rate capacity and excellent cycling stability.