Recent Advances in Conversion-Type Electrode Materials for Post Lithium-Ion Batteries

With the rapid expansion of electric vehicles and energy storage markets, the rising demand for rechargeable lithium-ion batteries, as opposed to the limited reserves of lithium resources, poses a great challenge to the widespread penetration of this advanced battery technology. Some monovalent metals, such as sodium and potassium, and multivalent metals, such as magnesium, zinc, and aluminum, which are nontoxic and relatively abundant (compared to lithium), are considered as alternative guest ions to lithium ion, thus generating various new battery systems. However, the major obstacle to their large-scale applications has been a lack of suitable robust hosts to accommodate alkalis (Na+, K+) with large radius or multivalent ions (Mg2+, Zn2+, Al3+) with high electrostatic repulsions. Conversion-type materials provide a unique route to tackle this problem because of their special reaction mechanism, which is different from the traditional intercalation reaction, and flexibility for tuning operating voltage. In this Review, the superiority of conversion electrodes for post lithium-ion batteries is discussed in detail, and the recent progress of the newly developed ions batteries based on the conversion mechanism is comprehensively summarized. Finally, the remaining challenges and the perspectives on research directions of conversion electrodes are proposed to provide guidance for future materials engineering and battery design.