Conversion Mechanism-Driven Lithium Storage in Sr2CoMoO6 Double Perovskite for High-Performance Anode
Authors: Atif Shahan , Zhu Yunpei , Khan Yusuf , Sachdeva Dorothy , Alshareef Husam Niman , Barpanda Prabeer 
Published: December 2024

The dominance of graphite as the anode material in Lithium-ion batteries (LIBs) is challenged by its inherent limitations. The restricted theoretical capacity of 372 mAh/g impedes its ability to satisfy the escalating demands for high-energy density storage solutions [1-3]. Furthermore, lithium plating during cycling raises serious safety concerns, and graphite exhibits poor capacity retention at high current densities [4]. To address these shortcomings, the development of anode materials with superior capacity, exceptional cycling stability, and enhanced safety characteristics is of prime importance. Conversion reactions present a compelling strategy for achieving significantly higher capacities compared to the conventional intercalation/deintercalation mechanisms employed in commercial LIBs [5-6]. These reduction processes involve the transformation of the electrode material during discharge into metal nanoparticles dispersed within a Li2O matrix. This approach offers a promising avenue to overcome the limitations of traditional intercalation mechanisms. Perovskite frameworks, with their diverse functionalities and unique crystal structures, have emerged as attractive candidates for energy storage applications due to their inherent ability to accommodate a wide range of cations [7]. This structural flexibility allows for the design of materials with properties tailored for specific electrochemical applications. Double perovskites (DPs), a subclass of perovskites with ordered B-site cations, present a particularly promising avenue for exploration as anode materials.

This study investigates the electrochemical performance of Sr2CoMoO6 (SCMO), a novel double perovskite synthesized via both solution-combustion and solid-state methods, as a potential high-capacity anode material for LIBs. A systematic half-cell configuration was employed for the evaluation of its anodic behaviour. To gain a deeper understanding of the structure and morphology, a comprehensive suite of advanced characterization techniques, including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), was utilized.

SCMO exhibits exceptional electrochemical performance, demonstrating a superior reversible capacity of 575 mAh/g during the initial discharge cycle in LIBs. Notably, the material showcases remarkable cycling stability, retaining an impressive 540 mAh/g after 250 cycles at a current density of 100 mA/g. This excellent performance is achieved within a broad potential window of 0.01-2.5 V, signifying the versatility of our material for practical battery applications. Furthermore, SCMO demonstrates remarkable rate capability, maintaining stable capacity across a wide range of current densities. This highlights the ability to deliver high power output, a crucial parameter for various portable electronic devices. To gain deeper insights into the underlying lithium storage mechanism, ex situ characterization employing XRD, XPS, SEM, and TEM was performed after cycling. The analyses revealed a conversion-dominated process, where Sr2CoMoO6 undergoes reduction to dispersed CoO and MoO3 nanophases embedded within an electrochemically inactive Li2O matrix. This analysis suggests that the high capacity achieved by SCMO originates from the conversion reaction mechanism. These compelling findings strongly advocate for the strategic design of DPs that exploit conversion mechanisms for lithium storage. This approach offers a promising avenue to significantly enhance the overall electrochemical performance of DP electrodes in LIB applications. By harnessing the unique properties of DPs and optimizing the conversion reaction process, researchers can develop next-generation anode materials with superior capacity, exceptional cycling stability, and improved safety characteristics. This paves the way for the development of high-performance LIBs that can meet the demands of the ever-evolving energy landscape.

Figure 1