Enhancing reversibility of metal anode-based secondary batteries via interface modification

Abstract

As the demand for environmentally friendly energy increases, there is active research aimed at developing high-performance secondary batteries. Among these, lithium metal and zinc metal are recognized as representative candidates for the next generation of secondary battery anodes. In particular, lithium metal has garnered attention as the ultimate anode for secondary batteries due to its high theoretical capacity (3860 mAh g$^{-1}$) and low reduction potential (-3.04 V vs. SHE). However, the uneven deposition of lithium on the electrode surface can lead to short circuits between the cathode and anode, posing safety hazards. Additionally, the formation of a thick and uneven passivation layer (solid-electrolyte interface, SEI), coupled with continuous electrolyte decomposition, results in reduced Coulombic efficiency, leading to rapid degradation of the battery due to material and electrolyte losses. Similarly, in the case of zinc metal, despite its high capacity (819 mAh g$^{-1}$, 5855 mAh cm$^{-3}$) and the advantage of using a safe aqueous electrolyte, issues such as dendrite formation on the electrode surface and hydrogen evolution reactions due to water reduction lead to volume expansion of the battery and increased electrode resistance. To address these challenges, this dissertation focuses on maximizing the reversibility and cycle performance of next-generation secondary batteries by coating various functional materials on the metal cathode surface. Specifically, the introduction of a reactive polymer layer on lithium metal surfaces has been explored to form a highly ion-conductive sulfur-enriched SEI layer, promoting uniform lithium growth. Furthermore, the introduction of Lewis basic phosphorus-doped graphitic carbon nitride interfacial layer on lithium metal controls the lithium ion flux, inducing facile desolvation of electrolyte. Additionally, it maintains the high lithium affinity even after Li intercalation, thus facilitating uniform nucleation and growth of lithium. When introducing phosphorus-doped graphitic carbon nitride interfacial layer on zinc metal, similar effects has been observed, including uniform zinc ion flux and facile desolvation of electrolyte. This layer also increases active surface area at the electrode-interfacial layer interface after zinc intercalation, and rapid surface diffusion of adsorbed atoms, inducing uniform Zn growth even under high current density operation.