In this paper, we wish to present an overview of the research carried out in our laboratories with low-cost transition metal oxides (manganese dioxide, iron oxide and vanadium oxide) as active electrode materials for aqueous electrochemical supercapacitors. More specifically, the paper focuses on the approaches that have been used to increase the capacitance of the metal oxides and the cell voltage of the supercapacitor. It is shown that the cell voltage of an electrochemical supercapacitor can be increased significantly with the use of hybrid systems. The most relevant associations are Fe3O4 or activated carbon as the negative electrode and MnO2 as the positive. The cell voltage of the Fe3O4/MnO2 device is 1.8 V and this value was increased to 2.2 V by using activated carbon instead of Fe3O4. These two systems have shown superior behavior compared to a symmetric MnO2/MnO2 device which only works within a 1 V potential window in aqueous K2SO4. Furthermore, the activated carbon/MnO2 hybrid device exhibits a real power density of 605 W/kg (maximum power density =19.0 kW/kg) with an energy density of 17.3 Wh/kg. These values compete well with those of standard electrochemical double layer capacitors working in organic electrolytes.

http://ma.ecsdl.org/content/MA2005-01/35/1348.full.pdf

Nanostructured Transition Metal Oxides for Aqueous Hybrid Electrochemical Supercapacitors

Supercapacitors are increasingly used for energy conversion and storage systems in sustainable nanotechnologies. Graphite is a conventional electrode utilized in Li-ion-based batteries, yet its specific capacitance of 372 mA h g−1 is not adequate for supercapacitor applications. Interest in supercapacitors is due to their high-energy capacity, storage for a shorter period and longer lifetime. This review compares the following materials used to fabricate supercapacitors: spinel ferrites, e.g., MFe2O4, MMoO4 and MCo2O4 where M denotes a transition metal ion; perovskite oxides; transition metals sulfides; carbon materials; and conducting polymers. The application window of perovskite can be controlled by cations in sublattice sites. Cations increase the specific capacitance because cations possess large orbital valence electrons which grow the oxygen vacancies. Electrodes made of transition metal sulfides, e.g., ZnCo2S4, display a high specific capacitance of 1269 F g−1, which is four times higher than those of transition metals oxides, e.g., Zn–Co ferrite, of 296 F g−1. This is explained by the low charge-transfer resistance and the high ion diffusion rate of transition metals sulfides. Composites made of magnetic oxides or transition metal sulfides with conducting polymers or carbon materials have the highest capacitance activity and cyclic stability. This is attributed to oxygen and sulfur active sites which foster electrolyte penetration during cycling, and, in turn, create new active sites.

/pdf/advanced-materials-and-technologies-for-supercapacitors-used-4rybecybwk.pdf

Advanced materials and technologies for supercapacitors used in energy conversion and storage: a review

Recent advances in perovskite oxides for anion-intercalation supercapacitor: A review

Electrochemical energy storage (EES) plays an important role in personal electronics, electrified vehicles, and smart grid. Lithium-ion batteries (LIBs) and supercapacitors (SCs) are two of the most important EES devices that have been widely used in our daily life. The energy density of LIBs is heavily dependent on the electrode capacity, in which the charge storage proceeds mainly in three different mechanisms, that is, alloying, conversion, and intercalation. Conventional LIBs show high energy density, but the rate performance is usually unfavorable. As a comparison, the SCs, which store energy based on electrochemical double layer capacitance (EDLC) or surface Faradaic redox pseudocapacitance, shows outstanding rate performance, but the energy density is still much worse than LIBs. Recently, intercalation pseudocapacitance appears as a new type of EES mechanism which stores energy into the bulk of electrode through a battery-like intercalation process but behaves similar to an electrode of SCs (fast reaction kinetics). Such intercalation pseudocapacitance can effectively narrow the gap between SCs and LIBs in energy density and power density, providing a new opportunity for the development of advanced energy storage system with both high energy density and power density. Up to now, more and more reports about intercalation pseudocapacitive materials have been appeared in literature, however, a systematic analysis of the recent development in intercalation pseudocapacitance is still lack. In this article, we provided an in-time review of the recent progress in the understanding of intercalation pseudocapacitive process and the development of related electrode materials for EES. Importance was paid to the difference between Faradaic surface-redox pseudocapacitance and intercalation pseudocapacitance, as well between battery-like intercalation and pseudocapacitive intercalation. Both cation interaction (Li+ and Na+) and oxygen anion intercalation pseudocapacitance was summarized.

Intercalation pseudocapacitance in electrochemical energy storage: recent advances in fundamental understanding and materials development

Recent advances in perovskite oxides as electrode materials for supercapacitors

Rational design of La0.85Sr0.15MnO3@NiCo2O4 Core–Shell architecture supported on Ni foam for high performance supercapacitors

Ag nanoparticles decorated perovskite La0.85Sr0.15MnO3 as electrode materials for supercapacitors

Oxygen-vacancy abundant alpha bismuth oxide with enhanced cycle stability for high-energy hybrid supercapacitor electrodes.

Coaxial cable-like dual conductive channel strategy in polypyrrole coated perovskite lanthanum manganite for high-performance asymmetric supercapacitors.

Xucong Sun

Papers

Rational design of La0.85Sr0.15MnO3@NiCo2O4 Core–Shell architecture supported on Ni foam for high performance supercapacitors

Ag nanoparticles decorated perovskite La0.85Sr0.15MnO3 as electrode materials for supercapacitors

Oxygen-vacancy abundant alpha bismuth oxide with enhanced cycle stability for high-energy hybrid supercapacitor electrodes.

Coaxial cable-like dual conductive channel strategy in polypyrrole coated perovskite lanthanum manganite for high-performance asymmetric supercapacitors.

Silver decorated lanthanum calcium manganate for electrochemical supercapacitor