Micro-sized anode materials demonstrate greater potential for practical applications than nanomaterials in the aspects of volumetric energy density, coulombic efficiency, fabrication process, and cost. However, the huge volume changes of alloy anodes (up to ∼500%) during repeated charge/discharge has led to a series of challenging issues including pulverization of active material particles and delamination from current collectors, formation of thick and fragile solid-electrolyte interphase (SEI) and depletion of electrolytes, eventually leading to rapid cell degradation. Herein, we review recent progress of rational strategies to enable the use of microsized alloy anodes (Si, P, Sb, Sn, etc.) including electrolyte modulation, binder design and architecture engineering. We also provide perspectives on future directions and remaining challenges of microsized anodes towards practical applications.

The discharge and charge mechanisms of rechargeable Li-O₂ batteries have been the subject of extensive investigation recently. However, they are not fully understood yet. Here we report a systematic study of the morphological transition of Li₂O₂ from a single crystalline structure to a toroid like particle during the discharge–charge cycle, with the help of a theoretical model to explain the evolution of the Li₂O₂ at different stages of this process. The model suggests that the transition starts in the first monolayer of Li₂O₂, and is subsequently followed by a transition from particle growth to film growth if the applied current exceeds the exchange current for the oxygen reduction reaction in a Li-O₂ cell. Furthermore, a sustainable mass transport of the diffusive active species (e.g., O₂ and Li⁺) and evolution of the underlying interfaces are critical to dictate desirable oxygen reduction (discharge) and evolution (charge) reactions in the porous carbon electrode of a Li-O₂ cell.