Lead-Free Double Perovskite Cs₂NaErCl₆: Li⁺ as High-Stability Anodes for Li-Ion Batteries

Halide perovskite materials have been used in the field of lithium-ion batteries because of their excellent ion migration characteristics and defect tolerance. However, the current lead-based perovskites used for lithium-ion batteries are highly toxic, which may hinder the pace of further commercialization. Therefore, it is still necessary to develop a new type of stable and pollution-free perovskite anode material. Herein, we for the first time use a high-concentration lithium-ion doped rare-earth-based double perovskite Cs₂NaErCl₆:Li⁺ as the negative electrode material for a lithium-ion battery. Thanks to its excellent structure stability, the assembled battery also has high cycle stability, with a specific capacity of 120 mAh g^-1 at 300 mA g^-1 after 500 cycles with a Coulomb efficiency of nearly 100%. The introduction of a rare earth element in a lead-free double perovskite paves a new way for the development of novel promising anode materials in the field of lithium storage applications.