Oxygen-Storage Materials to Stabilize the Oxygen Redox Activity of Three-Layered Sodium Transition Metal Oxides

To double the energy density of lithium- and sodium-ion batteries there is a need to activate simultaneously cationic and anionic redox reactions at the intercalation-type electrodes. In contrast to the cationic redox activity, the oxygen redox activity enforces an enhancement in the surface reactivity of the oxides leading to their poor reversibility and cycling stability. Herein, we propose a new concept to stabilize oxygen redox activity by using oxygen-storage materials as an efficient buffer supplying and receiving oxygen during alkali ion intercalation. As a proof-of-concept, the study is focused on CeO2 as a modifier of sodium nickel-manganese oxide with a three-layer sequence, P3- Na2/3Ni1/2Mn1/2O2. The CeO2-modified P3Na2/3Ni1/2Mn1/2O2 displays a drastic increase in the reversible capacity following the order Na+ intercalation < Li+ intercalation < Li+,Na+ cointercalation.

Automated summary

To enhance the energy density of lithium and sodium ion batteries, both cationic and anionic redox reactions at intercalation-type electrodes need to be activated simultaneously. Oxygen redox activity can lead to poor stability due to increased surface reactivity of the oxides. Using oxygen-storage materials as buffers can help stabilize the oxygen redox activity and increase reversible capacity.