홍지현 교수

The high capacity of the layered Li–excess oxide cathode is always accompanied by extraction of a significant amount of oxygen from the structure. The effects of oxygen on the electrochemical cycling are not well understood. Here, the detailed reaction scheme following oxygen evolution was established using real-time gas analysis and ex situ chemical analysis of the surface of the electrodes. A series of electrochemical/chemical reactions involving oxygen radicals constantly produced and decompo

Recently Li1.2Ni0.2Mn0.6O2, one of the most promising cathode candidates for next generation Li rechargeable batteries, has been consistently investigated especially because of its high lithium storage capacity, which exceeds beyond the theoretical capacity based on conventional chemical concepts. Yet the mechanism and the origin of the overcapacity have not been clearly understood. Previous reports on simultaneous oxygen evolution during the first delithiation may only explain the high capacity

Abstract Utilizing redox‐active organic compounds for future energy storage system (ESS) has attracted great attention owing to potential cost efficiency and environmental sustainability. Beyond enriching the pool of organic electrode materials with molecular tailoring, recent scientific efforts demonstrate the innovations in various cell chemistries and configurations. Herein, recent major strategies to build better organic batteries, are highlighted: diversifying charge‐carrying ions, modifyin

Prelithiation is of great interest to Li-ion battery manufacturers as a strategy for compensating for the loss of active Li during initial cycling of a battery, which would otherwise degrade its available energy density. Solution-based chemical prelithiation using a reductive chemical promises unparalleled reaction homogeneity and simplicity. However, the chemicals applied so far cannot dope active Li in Si-based high-capacity anodes but merely form solid-electrolyte interphases, leading to only

Although often overlooked in anode research, the anode's initial Coulombic efficiency (ICE) is a crucial factor dictating the energy density of a practical Li-ion battery. For next-generation anodes, a blend of graphite and Si/SiO_<i>x</i> represents the most practical way to balance capacity and cycle life, but its low ICE limits its commercial viability. Here, we develop a chemical prelithiation method to maximize the ICE of the blend anodes using a reductive Li-arene complex solutio

The exceptionally high gravimetric capacity of lithium-excess layered cathodes (LLCs) has generated interest in their use in lithium-ion batteries (LIBs) for high-capacity applications. Their unique electrochemical and structural properties are responsible for this high capacity, which exceeds the theoretical redox capability of transition metal oxides and have been intensively investigated. However, various fundamental and practical challenges must be overcome before LLCs can be successfully co

Abstract Despite their high energy densities, Li‐rich layered oxides suffer from low capacity retention and continuous voltage decay caused by the migration of transition‐metal cations into the Li layers. The cation migration stabilizes oxidized oxygen anions through the decoordination of oxygen from the metal once the anions participate in the redox reaction. Structural disordering is thus considered inevitable in most Li‐rich layered oxides. However, herein, a Mg‐substituted Li‐rich layered ox

Abstract Although Li 2 MnO 3 exhibits high capacity via anionic oxygen redox, it suffers from rapid capacity decay owing to structural disordering accompanying irreversible Mn migration and O 2 release. To promote the reversibility of the anionic redox reaction, Li 1.8 Mg 0.3 Mn 0.9 O 3 as a novel cathode material, prepared by partially substituting Li + and Mn 4+ of Li 2 MnO 3 with the redox‐inactive Mg 2+ as a structural stabilizer is proposed. Li 1.8 Mg 0.3 Mn 0.9 O 3 delivers a high specific

Abstract The exploding electric‐vehicle market requires cost‐effective high‐energy materials for rechargeable lithium batteries. The manganese‐rich spinel oxide LiNi 0.5 Mn 1.5 O 4 (LNMO) can store a capacity greater than 200 mAh g −1 based on the multi‐cation (Ni 2+ /Ni 4+ and Mn 3+ /Mn 4+ ) redox centers. However, its practical capacity is limited to Ni 2+ /Ni 4+ redox (135 mAh g −1 ) due to the poor reversibility of Mn 3+ /Mn 4+ redox. This instability is generally attributed to the Jahn–Tell

Abstract Li‐rich layered oxide materials are considered promising candidates for high‐capacity cathodes for battery applications and improving the reversibility of the anionic redox reaction is the key to exploiting the full capacity of these materials. However, permanent structural change of the electrode occurring upon electrochemical cycling results in capacity and voltage decay. In view of these factors, Ti 4+ ‐substituted Li 2 IrO 3 (Li 2 Ir 0.75 Ti 0.25 O 3 ) is synthesized, which undergoe

Stabilizing lattice oxygen at the electrochemical interface of Li-/Mn-rich cathodes preferentially promotes layered-to-spinel phase transition and suppresses rocksalt phase formation, offering excellent capacity retention.