Low-temperature induced crystallographic orientation boosting Li storage performance of Na2MoO4·2H2O

The design and development of high-performance anodes pose significant challenges in the construction of next-generation rechargeable lithium-ion batteries (LIBs). Sodium molybdate dihydrate (Na₂MoO₄·2H₂O) has garnered increasing attention due to its cost-effectiveness, non-toxicity and earth abundance. To enhance the Li storage performance of Na₂MoO₄·2H₂O, a crystallographic orientation regulation strategy is proposed in this work. Initially, density functional theory calculations are carried out to demonstrate that the (020) crystal plane of Na₂MoO₄·2H₂O offers the lowest energy barrier for Li⁺ migration. Subsequently, the preferred crystallographic orientation of Na₂MoO₄·2H₂O crystal is tuned through a low-temperature recrystallization method. Furthermore, the microstructure and phase changes of Na₂MoO₄·2H₂O during the lithiation/de-lithiation process are studied using in situ and ex situ XRD tests, ex situ XPS and cyclic voltammetry to unravel its Li⁺ storage mechanism. Upon application as LIBs anode, the Na₂MoO₄·2H₂O single-crystal particles with a preferred (020) surface exhibit superior reversible capacity, high-capacity retention and high cycling stability. The enhanced Li storage performance should be attributed to the regulated crystallographic orientation and small changes in the crystal microstructure during the charge/discharge process, which facilitates Li⁺ migration and bolsters structural stability. Notably, this study introduces a novel concept and a simple synthesis method for the advancement of electrodes in rechargeable batteries.

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