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Synthesis of V‑MoS2 Layered Alloys as Stable Li-Ion Battery Anodes

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journal contribution
posted on 03.12.2019, 04:13 by Yu Lei, Kazunori Fujisawa, Fu Zhang, Natalie Briggs, Amir Reza Aref, Yin-Ting Yeh, Zhong Lin, Joshua A. Robinson, Ramakrishnan Rajagopalan, Mauricio Terrones
Layered MoS2 nanostructures are attractive candidates as high-capacity anodes for lithium-ion batteries (LIB). However, the low intrinsic electrical conductivity of MoS2 limits its rate performance. Herein, we demonstrate that the electrical conductivity of MoS2 can be significantly improved by adding V atoms substitutionally via a two-step approach that includes the electrodeposition of amorphous MoS2 followed by a solid-state reaction that is able to crystallize the layered material and introduce V atoms into the MoS2 lattice. This approach also has the following advantages: (i) electrodeposition is a scalable process for synthesizing MoS2 films directly on the current collectors and (ii) amorphous electrodeposited MoS2 is prone to be doped with heteroatoms, thus allowing extensive V solubility ranging from 3.8 to 17.6 atom % in MoS2. This incorporation of vanadium (V 17.6 atom %) significantly reduces the band gap of MoS2 from 1.56 to 0.90 eV. The improvement in the electrical conductivity and Li-ion diffusion of V-MoS2 alloys also increases the retention capacity at high current densities (1000 mA g–1) by more than 4 times that of MoS2, with stable cyclability at both 200 and 1000 mAh g–1. The improved rate performance and capacity retention of V-MoS2 indicate that transition-metal alloying offers a viable alternative strategy when designing high-performance LIB anodes.