The Synthesis And Adjustment Of Manganese Compounds For Application In Electrochemical Energy Storage

In modern society,great efforts have been devoted to exploring sustainable and renewable resource to cope with climate change and decreasing of fossil fuels.Thus environmentally friendly and high efficiency energy storage devices are urgently needed.Lithium ion batteries and electrochemical capacitors are two kinds of new energy storage systems with high performance and receiving more and more attentions.So far,a wide application including in portable electronics,hybrid electric vehicle,large industrial equipment etc.has been achieved for lithium ion batteries and electrochemical capacitors.The requirements of higher energy density,higher power density and longer cycle life are put forward for developing new generation energy storage devices.Transition metal oxides have excellent lithium storage performance as well as good capacitive properties.Mn₂O₃ is considered as a potential candidate for electrode material of lithium ion batteries due to its high theoretical specific capacitance,nature abundance and environmental friendliness.MnCO₃ is cost effective,easy preparared and proved to be possession favorable capacitive characteristics.The disadvantage of both materials is their low electric conductivity,which results in worse rate performance and cycle life.To address these problems mentioned above,extensive researches should be made into rationally design and modify electrode materials.The main contens of this paper are listed as follows:（1）Hollow Mn₂O₃ core–shell microspheres were successfully fabricated via a mixed method including a solution method and a subsequent thermal decomposition.Transmission electron microscopy showed that the average size of Mn₂O₃ cores was about 0.8 μm and their shell thickness was 120 nm.These hollow Mn₂O₃ core–shell microspheres as anode materials of lithium ion batteries exhibited a high specific capacity of up to 620 mA h g^-1 with a good cycling performance（500 cycles）,indicating that the hollow Mn₂O₃ core–shell microsphere material was a promising anode candidate for a highcapacity,low-cost,and environment-friendly lithium ion battery.The formation mechanism was studied in detail.（2）Ni-doped Mn CO₃ microspheres were successfully synthesized via a one-step mixed solvent-thermal method.The as-prepared samples were characterized by X-ray diffraction,scanning electron microscopy,transmission electron microscopy and N2 adsorption–desorption measurements.The fabricated Ni-doped MnCO₃ microspheres exhibited a higher specific capacity(510 F g^-1 at a current density of 1 A g^-1)than pure Mn CO₃(223 F g^-1).In addition,85.8 % of initial capacity was retained after 3000 cycles at a current density of 5 A g^-1,demonstrating a good cycling performance.These results suggested that Ni-doped MnCO₃ microspheres material was a promising candidate for high energy storage applications.Hence doping heterogeneous element with good electrical conductivity was an effective approach to improve the electrochemical performance of the electrode materials.