A multi-step discharge/charge model of Li O2 batteries coupled with electrolyte decomposition and carbon electrode corrosion reactions

Electrolyte decomposition and electrode corrosion stand as two primary side reactions in lithium‑oxygen (Li O 2 ) batteries during their discharge/charge cycles. In this work, a comprehensive Li O 2 battery model combining multi-step lithium peroxide (Li 2 O 2 ) formation, electrolyte decomposition, and electrode corrosion is proposed. Based on this model, the deposition behaviors and cycling performance of the Li O 2 battery under deep discharge/charge cycles are investigated. The stop of discharge is mainly ascribed to the loss of active surface area for the battery using tetraethylene glycol dimethyl ether (TEGDME) electrolyte, while both O 2 transport limitation and active surface area loss lead to the discharge termination for battery using dimethyl sulfoxide (DMSO) electrolyte. The incomplete decomposition of Li 2 O 2 and lithium carbonate (Li 2 CO 3 ) clogs electrode pores, leading to a continuous decline in the discharge capacity of the Li O 2 battery. For the TEGDME-based battery, the undecomposed Li 2 CO 3 gradually dominates the deposition with cycles, wherein electrode corrosion becomes the primary source of the undecomposed Li 2 CO 3 after 3 cycles. For the DMSO-based battery, undecomposed Li 2 O 2 is always a dominant trigger for battery discharge capacity degradation, although electrode corrosion remains a key contributor to Li 2 CO 3 generation. Despite the DMSO-based battery exhibiting lower rates of electrolyte decomposition and electrode corrosion, it demonstrates poorer cyclic performance than the TEGDME-based battery due to the generation of more toroidal Li 2 O 2 . Moreover, when the charging cut-off voltage is reduced to 4.2 V, discharge capacity diminishes more rapidly due to the increased accumulation of undecomposed Li 2 O 2 , despite suppressed Li 2 CO 3 deposition. Finally, the results confirm that thick electrodes lead to deteriorating cycling performance, stemming from increased discharge/charge overpotential and extended discharge/charge times, thus intensifying the side reactions. • A multi-step discharge/charge Li-O 2 battery model involving electrolyte decomposition and electrode corrosion reactions is proposed. • Deposition/decomposition behaviors of Li 2 O 2 and Li 2 CO 3 from different reaction pathways with cycles are explored. • Mechanisms of discharge capacity degradation and discharge/charge failure under different conditions are revealed.