Lovett Adam J, Füredi Máté, Bird Liam, Said Samia, Frost Brandon, Shearing Paul R, Guldin Stefan, Miller Thomas S
Electrochemical Innovation Lab, Department of Chemical Engineering, University College London, Torrington Place, London WC1E 7JE, United Kingdom.
The Faraday Institution, Quad One, Didcot OX11 0RA, United Kingdom.
ACS Electrochem. 2025 Feb 28;1(6):962-973. doi: 10.1021/acselectrochem.4c00230. eCollection 2025 Jun 5.
Silicon nitride (SiN ), a conversion-alloying lithium-ion battery electrode with excellent potential to replace silicon and graphite anodes, offers improved cycle stability and fast-charging capabilities. During the formation cycle(s), SiN irreversibly converts into a mixture of lithiated silicon and nitridosilicate matrix. However, beyond this basic understanding, there is limited fundamental insight into how the post-conversion structure results in improved electrochemical performance. This significantly hinders the optimization and commercialization prospects of SiN anodes. Herein, electrochemical atomic force microscopy is used to uncover the morphological and chemo-mechanical changes of SiN thin films during the conversion reaction. We elucidate that the post-conversion SiN forms silicon domains embedded within a matrix with a core-shell-like structure comprised of a stiff outer nitridosilicate surface and softer inner Si-rich core. The silicon domains that form have very stable dimensions (∼100 nm in diameter) that, crucially, remain smaller than the critical cracking threshold of silicon. This results in a more mechanically robust anode, anticipated to be free from the adverse effects of cracking, pulverization, and subsequent capacity fade. Our work marks an important advance in the fundamental understanding of silicon nitride anodes and offers a pathway to their incorporation into next-generation batteries.
氮化硅（SiN ）是一种具有取代硅和石墨负极巨大潜力的转化合金化锂离子电池电极，具有更好的循环稳定性和快速充电能力。在形成循环过程中，SiN 不可逆地转化为锂化硅和氮氧化硅基体的混合物。然而，除了这种基本认识之外，对于转化后结构如何导致电化学性能改善的基本见解有限。这严重阻碍了SiN 负极的优化和商业化前景。在此，采用电化学原子力显微镜揭示了SiN 薄膜在转化反应过程中的形态和化学机械变化。我们阐明，转化后的SiN 形成了嵌入基体中的硅域，该基体具有核壳状结构，由坚硬的外部氮氧化硅表面和较软的内部富硅核组成。形成的硅域具有非常稳定的尺寸（直径约100 nm），关键的是，其尺寸仍小于硅的临界开裂阈值。这导致阳极在机械上更坚固，预计不会受到开裂、粉化以及随后容量衰减的不利影响。我们的工作标志着在氮化硅负极的基本理解方面取得了重要进展，并为将其纳入下一代电池提供了途径。
