The Oxidized Ti2(Al/Sn)C Behavior as Anode for Lithium‐ and Sodium‐Ion Batteries: The Role of the MAX Phase Order

The present study is dedicated to investigation of the performance of oxidized Ti2(Al/Sn)C system (211 MAX phases) as anode for lithium and sodium ion batteries. Their behavior has been rationalized as function of the tin content and as function of the MAX phase order, with detailed comparison with the 312 MAX phase analog series.

In the recent framework of the studies of Sn-doped MAX phase materials for potential applications as negative electrode materials in alkaline-ion batteries, this work explores the potentiality of the pure 211 MAX phase Ti₂Al_(1–y)Sn _y compound through solid-state synthesis and subsequent thermal oxidation. A complete structural investigation through neutron diffraction and thermal operando synchrotron X-ray diffraction elucidates the phase evolution during oxidation. In coin cell tests against lithium, both samples demonstrate initial anodic capacities attributed to irreversible conversion reactions, followed by reversible alloying/dealloying mechanisms. Similarly, tests against sodium show comparable electrochemical behavior, albeit with lower capacities due to sodium's lower reactivity with Sn oxide. The capacity retention after cycling can be associated to the structural stability of the electrodes. Overall, this study has a place in the broader framework of the Sn-doped MAX phases investigation, and once more it underscores the importance of optimizing Sn oxide formation for enhanced electrochemical performance in both Li-ion and Na-ion batteries, with implications for future active materials design.

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