Selenium (Se), a congener of Sulphur (S), is widely used as a cathode material for high energy-density lithium-ion batteries, named Li–Se batteries. It has been found that nanostructured Se confined in carbonaceous can lead to significantly improved rate capability and cyclic performance. However, the underlying mechanism of carbon coatings in view of surface/interface electro-chemo-mechanical effect at nanoscale remains poorly unexploited. Herein, equipped with in-situ transmission electron microscopy (TEM), we have investigated the type of lithium ions transportation, phase transformation, and coupling mechanical behavior of carbon conformably coated Se nanowire (NW) cathode reacted with Li. Intriguingly, We find a unique lithiation mechanism that the “leapfrog phase transformation” occurs at interface between carbon coating and Se NW cathode. The increasingly accumulated Li ions in leapfrog buckled region as a new platform would react with Se to form crystalline Li₂Se from surface to interior. More importantly, this interfacial diffusion pathway of Li ions uniquely differs from the surface-coating directed Li transportation engineered where in Li ions initially diffuse into coatings and then react with core materials of electrodes. Furthermore, we note a threshold diameter region of Se NWs with ~ 115–120 nm, above which the uniform carbon coating (~ 8.5 nm) shows remarkable crack and even delimitation after fully lithiation form. These observations provide reliable guidelines for the design of high-performance lithium-ion batteries by interface and surface engineering.

硒（Se）是硫（S）的同源物，被广泛用作高能量密度锂离子电池（称为Li-Se电池）的阴极材料。已经发现，限制在碳质中的纳米结构的Se可以导致显着改善的速率能力和循环性能。然而，鉴于在纳米尺度上的表面/界面电化学化学作用，碳涂层的基本机理仍未得到充分利用。本文中，我们配备了原位透射电子显微镜（TEM），研究了与Li反应的碳适形涂覆的硒纳米线（NW）阴极的锂离子传输类型，相变和耦合机械性能。有趣的是，我们发现了一种独特的锂化机制，即在碳涂层和Se NW阴极之间的界面处发生了“跨越式相变”。从表面到内部₂ Se。更重要的是，这种锂离子的界面扩散路径与表面涂层定向锂运输工程的独特之处不同，后者是锂离子最初扩散到涂层中，然后与电极的核心材料发生反应的地方。此外，我们注意到Se NWs的阈值直径区域约为115-120 nm，在该阈值直径以上的区域，均匀的碳涂层（〜8.5 nm）在完全锂化后显示出明显的裂纹甚至划界。这些观察结果为通过界面和表面工程设计高性能锂离子电池提供了可靠的指导。