Reaction Mechanism and Structural Evolution of Tunnel‐Structured KCu 7 S 4 Nanowires in Li + /Na + ‐Ion Batteries

• Published in: Advanced functional materials Vol. 34; no. 46
• Main Authors: Zhang, Kuikui, Wang, Hui, Du, Xiaobing, Dai, Shuge, Wang, Ye, Xu, Tingting, Liu, Meilin, Cheng, Shaobo
• Format: Journal Article
• Language: English
• Published: 01.11.2024
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.202407105

Selecting suitable electrode materials for sodium‐ion batteries (SIBs) often relies on the experience gained from lithium‐ion batteries (LIBs), particularly in terms of thermodynamics. However, this approach may fall into a stagnant situation where the development of SIBs consistently lags behind that of LIBs due to the larger ionic radius of Na + . Accordingly, it is crucial to establish a dedicated selection rule specifically tailored for SIB electrodes to overcome this challenge. Herein, a screening method is proposed for SIB materials, where an ideal candidate shall form a stable intermediate transition phase with Na + . This phase acts as an important bridge that can regulate the insertion/extraction of charge carriers. Atomically resolved transmission electron microscopy demonstrates that KCu 7 S 4 can react with Na + to form a stable intermediate phase (Na 3 Cu 4 S 4 ). Na 3 Cu 4 S 4 can undergo reversible conversion reactions, contribute capacity, stabilize the tunnel structure and enhance the migration/diffusion of Na + . In contrast, Li + can't form a stable intermediate phase in KCu 7 S 4 during lithiation/delithiation, thus losing the ability to effectively regulate Li + insertion/extraction. These findings provide valuable insights for the development of suitable electrode materials for SIBs, emphasizing the importance of stable intermediate phases in regulating charge carrier insertion/extraction and improving overall battery performance.