Two-dimensional transition metal dichlorides (MCl2, M = Fe, Ni, and Zn) as prominent anode materials for Li/Na ion batteries: a computational study

With advances in energy storage technologies and a growing demand for flexible batteries, the development of high-performance 2D anode materials has become crucial for enhancing the performance of rechargeable batteries. Herein, the potential of metal chlorides MCl₂ (M = Fe, Ni, and Zn) as anode materials for Li/Na ion batteries was investigated using density functional theory (DFT). The results showed that MCl₂ monolayers exhibit robust kinetic stability, favorable thermodynamic adsorption of Li/Na ions, and a higher adsorption strength for Li compared to Na ions. Charge transfer analysis reveals that Li/Na ions donate electrons to the MCl₂ monolayers, thereby altering their electronic structure. Band structure calculations show that, following Li/Na adsorption, FeCl₂ and NiCl₂ monolayers transition from semiconductors to metals, enhancing material conductivity and facilitating ion diffusion. Remarkably, the diffusion energy barriers for Li/Na ions in FeCl₂ and NiCl₂ are below 0.20 and 0.10 eV, respectively, thus ensuring the rapid Li/Na ion migration in the two materials. More importantly, further computations revealed that NiCl₂ exhibits a high theoretical storage capacity (827.26 mAh g⁻¹) and a low open-circuit voltage (Li/Na: 0.13/0.11 V), suggesting its great potential for application as an anode material. Our findings not only suggest a promising anode material, but also broaden the application potential of metal chlorides in energy storage.