Revealing oxygen release suppression in Co-free Li-rich layered oxides via Mo doping through direct gas analysis

초록

Cobalt-free lithium-rich layered oxides (LLOs) are promising high-energy cathodes, yet their practical application is hindered by irreversible oxygen release and consequent gas evolution during activation and long-term cycling. Such gas generation becomes more severe under realistic full-cell conditions, while direct quantitative verification has remained limited. Herein, we propose a Mo-doping strategy to stabilize oxygen activity in Co-free Mn-rich LLOs and directly validate its effect in pouch full-cells. Owing to the strong Mo-O bonding and appropriate ionic characteristics of Mo6+, lattice oxygen stability is enhanced, mitigating irreversible oxygen redox reactions and promoting structural robustness. The Mo-doped LLO delivers a high initial discharge capacity of 253.0 mAh g- 1 with improved cycling stability. More importantly, gas evolution was quantitatively analyzed in pouch full-cells at elevated temperature using the Archimedes method combined with gas chromatography. The Mo-doped sample exhibits an approximately 81.0% reduction in total gas generation after 150 cycles compared with the pristine material, including complete elimination of CO and significant suppression of CO2 and hydrocarbon species. These results provide direct experimental evidence that Mo doping effectively suppresses oxygen-triggered degradation, offering a practical oxygen-release-controlled design strategy for Co-free LLO cathodes.

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