Unraveling structure evolution failure mechanism in MoS2 anode for improving lithium storage stability

2H phase molybdenum disulfide (2H-MoS2) possesses the two-dimensional layered structure and high theoretical capacity, presenting excellent lithiation-delithiation property. However, the violent capacity decay within dozens of cycles still remains a great challenge due to lacking of in-depth failure mechanism. Herein, a novel decay-recovery-decay failure phenomenon upon long-term cycles is reported for the first time, which originates from the slow size change of Mo nanoparticles (NPs). Decay stages are triggered by many irregular-shaped Mo NPs with the increasing size up to similar to 15 nm, leading to prominent pseudocapacitance failure and capacity loss. Subsequent recovery stages are attributed to the pulverization of coarse Mo NPs through surface sulfurization and accompanying lithiation. To overcome the instability issue, proper modifiers should be introduced to restrain the spontaneous growth of Mo NPs, such as aluminum oxide (Al2O3). The strong Mo-Al2O3 bond gradually "drags" Al2O3 fragments into the active material as the cycle continuously proceeds, resulting in the efficient refinement and the reversible conversion between Mo and MoS2. Therefore, the enhanced cycling stability and the capacity retention are successfully achieved. It is expected to provide a new insight into the energy storage of transition metal chalcogenide anode materials in rechargeable batteries. (C) 2022 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.