Lim, Gukhyun Cho, Min Kyung Choi, Jaewon Zhou, Ke-Jin Shin, Dongki Jeon, Seungyun Kwon, Minhyung Jeon, A-Re Choi, Jinkwan Sohn, Seok Su Lee, Minah Hong, Jihyun 2024-11-30T06:30:18Z 2024-11-30T06:30:18Z 2024-11-30 2024-12 1754-5692 https://pubs.kist.re.kr/handle/201004/151221 Exploiting oxygen anion redox in Li-/Mn-rich layered oxides (LMR-NMCs) offers the highest capacity among cathode materials for Li-ion batteries (LIBs). However, its long-term utilization is challenging due to continuous voltage and capacity decay caused by irreversible phase transitions involving cation disordering and oxygen release. While extensive studies have revealed the thermodynamic origin of cation disordering, the mechanisms of oxygen loss and consequent lattice densification remain elusive. Moreover, mixed spinel-rocksalt nanodomains formed after cycling complicate the degradation mechanism. Herein, we reveal a strong correlation between phase transition pathways and oxygen stability at the particle surface in LMR-NMCs through a comparative study using electrolyte modification. By tailoring surface reconstruction pathways, we control the overall phase and electrochemistry evolution mechanisms. Removing polar ethylene carbonate from the electrolyte significantly suppresses irreversible oxygen loss at the cathode–electrolyte interface, preferentially promoting the in situ layered-to-spinel phase transition while avoiding typical rocksalt phase formation. The in situ formed spinel-stabilized surface enhances charge transfer kinetics through three-dimensional ion channels, maintaining reversible Ni, Mn, and O redox capability over 700 cycles, as revealed by electron microscopy, X-ray absorption spectroscopy, and resonant inelastic X-ray scattering. Deep delithiation and lithiation enabled by the surface spinel phase accelerate the bulk layered-to-spinel phase transition, inducing thermodynamic voltage fade without capacity loss. Conversely, conventional electrolytes induce layered-to-rocksalt surface reconstruction, impeding charge transfer reactions, which causes simultaneous capacity and (apparent) voltage fades. Our work decouples thermodynamic and kinetic aspects of voltage decay in LMR-NMCs, establishing the correlation between surface reconstruction, bulk phase transition, and the electrochemistry of high-capacity cathodes that exploit cation and anion redox couples. This study highlights the significance of electrochemical interface stabilization for advancing Mn-rich cathode chemistries in future LIBs. English Royal Society of Chemistry Decoupling capacity fade and voltage decay of Li-rich Mn-rich cathodes by tailoring surface reconstruction pathways Article 10.1039/d4ee02329c 1 Energy & Environmental Science, v.17, no.24, pp.9623 - 9634 Energy & Environmental Science 17 24 9623 9634 N scie scopus 001358704900001 2-s2.0-85209721816 Chemistry, Multidisciplinary Energy & Fuels Engineering, Chemical Environmental Sciences Chemistry Energy & Fuels Engineering Environmental Sciences & Ecology Article LAYERED COMPOSITE CATHODE REDOX CHEMISTRY OXIDE HYSTERESIS ELECTRODES ORIGIN