Stabilizing Lattice Oxygen Redox Through Bicarbonate Pyrolysis-Driven Multifunctional Interface Engineering in...

Li-rich layered oxides (LRs) are promising candidates for high-capacity cathodes in next-generation lithium-ion batteries (LIBs). However, their commercialization faces challenges such as rapid capacity fading, voltage decay, and irreversible oxygen release. In this study, we develop an innovative interface engineering driven by bicarbonate pyrolysis, which constructs a coherent spinel-phase surface layer, generates abundant oxygen vacancies, and facilitates near-surface metal ion doping (K⁺, Na⁺, or Mg²⁺) on LRs. These enhancements work synergistically to significantly boost the electrochemical performance of the cathode. Notably, the optimized KHCO₃-treated sample (SK-LR) exhibits outstanding cycling stability, retaining 94.9% of its capacity after 500 cycles at 1C and 98.9% after 100 cycles at 0.1C, compared to only 67.8% and 85.5% retention for the pristine cathode. Furthermore, SK-LR achieves a high energy density of 1 110.5 Wh kg^-1, along with superior rate capability and thermal stability. Through ex/in situ characterizations and theoretical calculations, this interface engineering is evidenced to be effectively stabilize lattice oxygen by increasing oxygen vacancy formation energy from 3.87 to 5.34 eV, enhancing crystal structure via strengthened Mn─O bonds, and optimizing Li⁺/e^- transport kinetics. This work presents effective interfacial engineering to develop ultra-stable Li-rich cathodes, offering a viable pathway for advancing high-energy density LIBs.