Tham khảo tài liệu 'energy storage in the emerging era of smart grids part 2', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 18 Energy storage in the Emerging Era of Smart Grids Nanostructured redox materials Since in pseudo-capacitors the charge accumultes on the first nanometers of the surface by reducing the particle dimension the active surface of the material increases. For example MnC 2 and RuC 2 films deposited on different supports metal collectors carbon nanotubes active carbon have shown specific capacitance values higher than 1300 F g1. It has been demonstrated that the synthesis of thin films or the decoration of high SSA capacitive materials with pseudo-capacitive materials increases the energy density. Fig. 11. Possible strategies to enhance esTgy and specific power of electrochemical capacitors a b decoration of active carbongrains a with pseudo capacitive materials b . c d attainment of an uniform deposit of ps eudo-capacitive material d on high ordered high SSA CNT layer c . Hybrid systems Hybrid systems offer a valid alternative to traditional pseudo-capacitors or EDLC allowing to combine in the same cell one battery-type electrode energy source with one capacitortype electrode power source . At present two different approaches have been adopted i metal oxide electrode having pseudo-capacitive properties with a capacitive carbon electrode and ii lithium-inserted electr ode with capacitive carbon electrode. Several combinations of positive and negative electrodes have been investigated in aqueous and organic electrolytes. In most cases the fardic electrode produced an increase in energy density but a decrease in cyclability. This is certainly the main drawback of hybrid devices in comparison with EDLC. Electrochemical energy storage 19 MnC 2 represents a valid alternative to R11O2 due to its low cost. Its pseudo-capacitance originates from the change in oxidation state lll IV at the MnO 2 particle surface. The association of a negative EDLC-type electrode with a positive MnC 2 one produces a 2V cell in aqueous electrolyte thanks to the overvoltage of water .
