In situ-formed C-N anchors embedded into Sn-based negative electrodes for long-life Na-ion batteries

Limited cycle life remains a major obstacle to the practical application of high-capacity alloy negative electrodes in rechargeable batteries aimed at boosting energy density. The key challenges lie in the inherent uncontrollable volume changes and unstable electrode-electrolyte interphases. Here, we demonstrate a long-life self-construal tin (Sn) negative electrode for sodium (Na)-ion batteries enabled by in situ-formed embedded C-N anchors that integrate mechanical and chemical restrictions. This effect reshapes the alloying reactions with pronounced phase transformation hysteresis and triggers an electrochemically driven self-reconstructed structure for alloying reactions, therefore resolving the uncontrollable volume expansion and associated detrimental effects. C-N anchors also promote the formation of unique viscoelastic electrode-electrolyte interphases that comfortably accommodate large volume fluctuations for thousands of cycles. The designed Sn-based negative electrode exhibits long cycle life over 7000 cycles with a low-capacity decay rate of ~0.0036% at 2 C. Stable cycling of the Sn-based negative electrode is further confirmed in a prototype Na-ion pouch cell. This work offers an efficient design of employing the inherent volume expansion of alloy to electrochemically induce a self-constructed structure that comfortably accommodates volume changes, thereby ensuring long cycle life.