Meaning
Irreversible structural decomposition in highly oxidized transition metal oxide cathodes releases gaseous oxygen from the crystal frame into cell interiors during high-voltage charging. The occurrence of lattice oxygen degassing reduces active material stoichiometry while generating volatile species that build internal pressure inside sealed electrochemical cells. This gas evolution phenomenon marks a fundamental degradation threshold for high-energy lithium batteries operating above critical oxidation potentials.
Phase Transformation
Oxidation of lattice oxygen ions to peroxides or molecular gas triggers a irreversible transition from layered crystal structures to rock-salt or spinel phases. During extreme electrochemical extraction, lattice oxygen degassing leads to surface restructuring that impedes lithium ion diffusion through damaged transition metal layers. Loss of structural oxygen leaves vacant lattice sites, accelerating transition metal dissolution into organic liquid electrolytes.
Microcracking degrades grain boundaries.
Thermal Instability
Released oxygen gas reacts exothermically with flammable organic electrolyte solvents inside closed cell casings. When lattice oxygen degassing occurs at elevated temperatures, local heat generation triggers self-sustaining thermal runaway cascades.
Mitigation Strategy
Surface modification techniques prevent oxygen release by stabilizing transition metal bonds at high state of charge. Applying protective coating layers or doping crystal structures with titanium strengthens metal-oxygen bonds to suppress lattice oxygen degassing during high-voltage operation. Doped layered oxides retain structural integrity across extended cycling.
