Trifunctional L-Cysteine Assisted Construction of MoO 2 /MoS 2 /C Nanoarchitecture Toward High-Rate Sodium Storage.

The volume collapse and slow kinetics reaction of anode materials are two key issues for sodium ion batteries (SIBs). Herein, an "embryo" strategy is proposed for synthesis of nanorod-embedded MoO 2 /MoS 2 /C network nanoarchitecture as anode for SIBs with high-rate performance. Interestingly, L-cysteine which plays triple roles including sulfur source, reductant, and carbon source can be utilized to produce the sulfur vacancy-enriched heterostructure. Specifically, L-cysteine can combine with metastable monoclinic MoO 3 nanorods at room temperature to encapsulate the "nutrient" of MoO x analogues (MoO 2.5 (OH) 0.5 and MoO 3 ·0.5H 2 O) and hydrogen-deficient L-cysteine in the "embryo" precursor affording for subsequent in situ multistep heating treatment. The resultant MoO 2 /MoS 2 /C presents a high-rate capability of 875 and 420 mAh g -1 at 0.5 and 10 A g -1 , respectively, which are much better than the MoS 2 -based anode materials reported by far. Finite element simulation and analysis results verify that the volume expansion can be reduced to 42.8% from 88.8% when building nanorod-embedded porous network structure. Theoretical calculations reveal that the sulfur vacancies and heterointerface engineering can promote the adsorption and migration of Na + leading to highly enhanced thermodynamic and kinetic reaction. The work provides an efficient approach to develop advanced electrode materials for energy storage.