C. Wang, Y.X. Ning, H.B. Huang, S.W. Li, C.H. Xiao, Q. Chen, L. Peng, S.N. Guo, Y.F. Li, C.H. Liu, Z.-S. Wu, X.F. Li, L.W. Chen, C. Gao, C. Wu, Q. Fu*

National Science Review, 2021, 8, nwaa289.

DOI: 10.1093/nsr/nwaa289 [PDF]

Methodology of modern surface chemistry has been applied for visualization of electrochemical processes at operating electrode surfaces in an Al/graphite model battery. Intercalation of anions together with cations is directly observed in surface region of the graphite electrode with tens of nanometers thickness, whose concentration is amazingly one order higher than that in bulk. An intercalation pseudocapacitance mechanism and a double specific capacity in the electrode surface regions are derived based on the super-dense intercalants and anion/cation co-intercalation phenomena, which are well verified by performance tests of real devices using nanometer thick graphite cathode outperforming that using micrometer thick graphite cathode. Our findings highlight the important roles of electrode surface or thickness effect in charge storage systems.