Porous alloying-type particles for practical lithium-ion battery anodes

Li-alloying-type anodes (Si, Sn, Ge, etc.) are potential candidates for high-energy lithium-ion batteries (LIBs), offering outstanding Li-storage capacity. However, their practical use is hampered by severe volume fluctuations during cycling, which lead to particle pulverization, an unstable interphase, and thus a shortened lifespan. Engineered porous structures have emerged as being key to solving these challenges. This review focuses on the porous alloying-type particles (ATPs) for LIB anodes. First, the structural evolution of ATPs with or without pores during lithiation is analysed using a graphite anode as a reference, highlighting the critical role of intraparticle rather than interparticle pores. Synthetic methodologies for fabricating porous ATPs are summarized and categorized into bottom-up, top-down, and transcription approaches, with special emphasis on their scalability for practical application. Recent progress in elucidating the in-cell evolution of pores and the key function of intraparticle pores is discussed in detail, emphasizing the contrasting effects of open versus closed pores. We also review representative diagnostic techniques for quantitative pore characterization, and the advanced binders or electrolytes that stabilize porous ATPs in the context of practical pouch or cylindrical cells. Lastly, we discuss cell-level considerations and operating procedures, outlining future research directions toward post-intercalation anodes for both liquid- and solid-state LIBs.