Wang Xinyu, Yang Lei, Liang Huanyu, Zhu Chunliu, Shi Jing, Wu Jingyi, Chen Jingwei, Tian Weiqian, Zhu Yue, Wang Huanlei
School of Materials Science and Engineering, Ocean University of China, Qingdao, 266100, China.
Small. 2024 Dec;20(49):e2406577. doi: 10.1002/smll.202406577. Epub 2024 Sep 9.
The poor cycling stability and rate performance of transition metal selenides (TMSs) are caused by their intrinsic low conductivity and poor structural stability, which hinders their application in potassium-ion batteries (PIBs). To address this issue, encapsulating TMSs within carbon nanoshells is considered a viable strategy. However, due to the lack and uncontrollability of internal void space, this structure cannot effectively mitigate the volume expansion induced by large K, resulting in unsatisfactory electrochemical performance. Herein, peanut-shaped FeSe@carbon yolk-shell capsules are prepared by modulation of the internal space. The active FeSe is encapsulated within a robust carbon shell and an optimal void space is retained between them. The outer carbon shell promotes electronic conductivity and avoids FeSe aggregation, while the internal void mitigates volume expansion and effectively ensures the structural integrity of the electrode. Consequently, the FeSe@carbon anode demonstrates exceptional rate performance (242 mAh g at 10 A g) and long cycling stability (350 mAh g after 500 cycles at 1 A g). Furthermore, the effect of internal space modulation on electrochemical properties is elucidated. Meanwhile, ex situ characterizations elucidate the K storage mechanism. This work provides effective guidance for the design and the internal space modulation of advanced TMSs yolk-shell structures.
过渡金属硒化物（TMSs）较差的循环稳定性和倍率性能是由其固有的低电导率和较差的结构稳定性所致，这阻碍了它们在钾离子电池（PIBs）中的应用。为了解决这一问题，将TMSs封装在碳纳米壳内被认为是一种可行的策略。然而，由于内部空隙空间的缺乏和不可控性，这种结构无法有效缓解由大尺寸钾离子引起的体积膨胀，导致电化学性能不尽人意。在此，通过调控内部空间制备了花生状的FeSe@碳蛋黄壳胶囊。活性FeSe被封装在坚固的碳壳内，且它们之间保留了最佳的空隙空间。外部碳壳提高了电子导电性并避免了FeSe的聚集，而内部空隙则减轻了体积膨胀并有效确保了电极的结构完整性。因此，FeSe@碳负极展现出优异的倍率性能（在10 A g下为242 mAh g）和长循环稳定性（在1 A g下循环500次后为350 mAh g）。此外，阐明了内部空间调控对电化学性能的影响。同时，非原位表征揭示了钾存储机制。这项工作为先进的TMSs蛋黄壳结构的设计和内部空间调控提供了有效的指导。
