Riemannian Surface on Carbon Anodes Enables Li-Ion Storage at -35 °C.

Since sluggish Li desolvation leads to severe capacity degradation of carbon anodes at subzero temperatures, it is urgently desired to modulate electron configurations of surface carbon atoms toward high capacity for Li-ion batteries. Herein, a carbon-based anode material (O-DF) was strategically synthesized to construct the Riemannian surface with a positive curvature, which exhibits a high reversible capacity of 624 mAh g with an 85.9% capacity retention at 0.1 A g as the temperature drops to -20 °C. Even if the temperature drops to -35 °C, the reversible capacity is still effectively retained at 160 mAh g after 200 cycles. Various characterizations and theoretical calculations reveal that the Riemannian surface effectively tunes the low-temperature sluggish Li desolvation of the interfacial chemistry via locally accumulated charges of non-coplanar sp (2 < < 3) hybridized orbitals to reduce the rate-determining step of the energy barrier for the charge-transfer process. Ex-situ measurements further confirm that the sp -hybridized orbitals of the pentagonal defect sites should denote more negative charges to solvated Li adsorbed on the Riemannian surface to form stronger Li-C coordinate bonds for Li desolvation, which not only enhances Li-adsorption on the curved surface but also results in more Li insertion in an extremely cold environment.