Super-theoretical capacity mechanism of hollow nano-corn cob-like cobalt oxide

Abstract The capacity densities of hollow nano-corn cob-like cobalt oxide (HNc-Co3O4) during the 1st and 78th cycles in lithium-ion batteries (LIBs) are 1887 and 900 mAh g−1, respectively, with a coulombic efficiency of ∼ 98%. The electrochemical mechanism of the exciting, outstanding super-theoretical capacity (STC) can not only improve the capacity density but also exceed the current limit of LIBs. STC is commonly achieved during the conversion reaction of the electrodes in LIBs, and it is necessary to explore the source of the STC and determine how to maintain this level of capacity. The STC of HNc-Co3O4 is mainly due to the reversible reaction of ROCO2Li in the solid electrolyte interphase (SEI), pseudocapacitance at the Li2O/Co interface, and the contribution of carbon at low potentials. Regulating the composition of the SEI is very important for maintaining the STC, as it improves the cycle life and capacity density of the HNc-Co3O4 electrode. The analysis of the contribution and influencing factors of the STC for Co3O4 has guided the analysis of the additional lithium storage behavior of other metal oxides, and it is beneficial for increasing the energy density and power density and promotes the commercialization of conversion-type reaction electrode materials.