Cu-catalyzed carbonization microenvironment enables interfacial coupling in silicon-graphite anodes

Commercial silicon-graphite anodes typically restrict the silicon fraction below 10 % to preserve structural integrity, yet this compromises their energy density. When the silicon content rises to ∼20 %, the severe volume mismatch between silicon and graphite generates interfacial delamination, SEI overgrowth, and rapid capacity decay. Conventional carbon coatings fail to resolve this conflict—soft carbons creep plastically, while hard carbons are rigid but disordered, causing brittle fracture and weak interfacial bonding. Here, we introduce a Cu-regulated carbonization microenvironment strategy to construct a robust silicon-graphite composite. Trace Cu catalytically redirects the pyrolysis of glucose toward aromatization-graphitization, yielding a high- sp 2 , densely stacked carbon sheath with superior conductivity and mechanical strength. Simultaneously, Cu acts as a chemical welder, weakening Si–Si bonds and inducing covalent Si–C/Si– O –C linkages that anchor the carbon shell to the active core. The resulting Cu-templated composite maintains structural integrity and achieves 94.3 % capacity retention after 600 cycles at 0.2 A g −1 . This work establishes a dual catalytic-interfacial function of Cu, offering a new paradigm for carbon microenvironment regulation in high-silicon composite anodes.