Robust Silicon-Based Anode with High Energy Density upon Dual Welding Encapsulation.

Silicon has long been considered one of the most promising anode materials for high-performance lithium-ion batteries due to its high theoretical capacity. However, a significant challenge that restricts its practical application is the persistent issue of weak interfacial contact in the silicon anode, which leads to structural instability during lithiation/delithiation processes due to large volume expansion. In this work, we develop a dual welding encapsulation strategy by constructing Si-C chemical bonding between the silicon and conductive covering shells and establishing C-C interlayer bonding connections among the covering shells. By directly examining the interface of silicon-based composites, we identify the types of compounds and hybrid orbital structures from their spatial distribution using machine-learning-enhanced transmission electron microscopy analysis techniques. This dual welding mechanism not only enhances the mechanical strength of the protective carbon shell but also ensures sustained electrical connection between the core and shell through the Si-C bonds. The robust heterogeneous structure effectively mitigates interfacial instability within the silicon anode, suppressing volume expansion below 12% after 300 cycles. Thus, the full-cell with the composite anode and LiNi0.8Co0.1Mn0.1O2 cathode performs a high energy density of 576 Wh kg-1 and stable cycling, inspiring the construction of commercial silicon batteries.