Scientists Identify Oxygen Trapping Weakens Sodium-Ion Battery Performance

Professor Li Chao, working at ECNU, found that the oxygen trapping in the high-sodium P2-type layered oxide cathodes is the foremost culprit for voltage degradation. Taking advantage of the electron paramagnetic resonance (EPR) spectroscopy at the Steady-State Strong Magnetic Field Facility, Chinese Academy of Sciences, they monitored the dynamics of oxygen species observed and connected them with structural degradation. Reported in the journal Advanced Energy Materials, the discovery offers new insight for building more stable cathodes for sodium-ion batteries – an important goal in enabling smaller-scale energy storage applications and renewable energy technologies.

Oxygen Trapping Identified as Key Factor Behind Voltage Loss in High-Sodium Cathodes

According to the Advanced Energy Materials report, the researchers noted that as the cathode is used, oxygen in it reduces to form molecular O2, which some gets retained in a discharged state over several cycles.

This uncontrollable oxygen growth was pinned as the dominant origin of U loss and capacity decay. EPR measurements also revealed local structural differences, such as the phase separation of lithium- and manganese-rich phases, which would accelerate cycling degradation.

The team explained that high-sodium-content cathodes, with insufficient interlayer spacing, are more prone to oxygen trapping compared to low-Na counterparts. Low-Na materials' wider spacing lets oxygen migrate safely, preventing degradation, emphasising interlayer engineering's role in battery stability.

Real-time EPR provided a means to follow reactive intermediates and was used to direct approaches for voltage fade reduction and cathode performance enhancement. The research provides a new opportunity for the design of high-performance sodium-ion batteries for renewable energy storage, electric vehicles, and large-scale applications. The new batteries should last longer than the current ones by avoiding oxygen trapping and maintaining much more energy capacity for more charge-discharge cycles.