The limitation mechanisms on the discharge behavior of Li-O2 batteries.

• A hybrid model of Li-O 2 battery is developed with the morphological evolution of the cathode pore structure. • Mechanisms of discharge failure under different conditions are revealed. • Evolution of the cathode pore structure morphology needs to be considered for the cathode made of small-sized CNP or CNT. A comprehensive model for lithium-oxygen (Li-O 2) batteries is proposed and the discharge performance across varying cathode thickness, porosity, and pore structural evolution modes is thoroughly investigated. The results reveal that the cathode surface passivation restricts the discharge capacity but promotes the uniform distribution of lithium peroxide (Li 2 O 2), especially near the O 2 side. The electrode thickness of 255 μm serves as the boundary point between the two limiting mechanisms, with thicker electrodes primarily governed by O 2 diffusion and thinner ones by surface passivation. In addition, a novel hybrid model is proposed with the morphological change of the cathode pore structure, which can predict the discharge performance made of different carbon materials, proving its superiority over the commonly used Single model. The maximum discharge capacities of carbon nanoparticle (CNP)- and carbon nanotube (CNT)-based cathodes are obtained at the radius of CNP and CNT of 30 nm and 20 nm, respectively. The superiority of discharge performance of the CNP-based cathode over the CNT-based cathodes becomes more pronounced as the carbon material radius increases. The evolution of the cathode pore structure morphology needs to be considered for the cathode made of small-sized CNP or CNT, such as r CNP = 10 nm and r CNT = 20 nm. [ABSTRACT FROM AUTHOR]