Research On The Preparation Of Algae-based Carbon/manganese Oxide Composite Material And Its Energy Storage Performance

Due to the lack of global energy and the destruction of environment,the major challenge faced by human beings in today's society is to develop energy storage equipment and energy materials with the characteristics of clean,efficient,low cost,and renewable.Both supercapacitors and lithium-ion batteries are promising alternative energy storage devices.For these two new energy storage devices,improving the electrochemical properties of electrode materials is the key to improve their capacities and cycle lives.Biomass carbon materials are the new and renewable energy materials.As the typical aquatic plants,seaweeds are the ideal raw materials for the preparation of biomass carbon materials due to its wide source and low price.However,pure carbon materials such as carbon nanotubes,carbon fiber cloth,carbon black,and others have the disadvantage of low capacity.For instance,the theoretical specific capacitance of porous carbon material is only 250 F g^-1 when the specific surface area is 1000 m² g^-1.Manganese oxide is considered to be one of the most potential electrode materials because of its advantages of low cost,friendly environment,rich resources,and high theoretical capacity.However,the manganese oxide has a lower conductivity,which leads to the reduction of its capacity and cycle life,limiting its application on the electrode material.A feasible strategy to overcome the above problems is to compounded the manganese oxide with carbon to prepare the composites of the two.In this way,the good electrical conductivity and chemical stability of carbon can combine with the high capacity of manganese oxide.So the composites can both have good stability and high capacity.In this paper,seaweeds were used as the carbon sources.Carbon and manganese oxide were in-situ combined by simple wet chemical reaction,hydrothermal,ion exchange,and so on.The electrochemical properties of composites were studied by supercapacitors?SCs?or lithium-ion batteries?LIBs?.Therefore,this paper contains the following aspects of research work.?1?A carbon substrate?AC prepared from enteromorpha prolifera?ACEP??with typical hierarchical micro-/meso-/macro porous structure was prepared by pyrolysis and activation of enteromorpha prolifera?EP?and was used to deposit MnO₂ nanostructures via simple wet chemical reaction process.A series of characterizations for the structure and morphology of the ACEP@MnO₂ composites were carried out.Besides,the electrochemical properties were tested and studied by using the ACEP@MnO₂ composites as supercapacitor electrode materials.?2?The MnCO₃@C precursors were synthesized via a simple hydrothermal method with the sodium alginate?SA?as carbon source and the MnO@C-AH composites containing oxygen vacancy defects were obtained by pyrolyzing and resducing the MnCO₃@C precursors under Ar/H₂ atmosphere.A series of characterizations for the structure and morphology of the MnO@C-AH composites were carried out.Moreover,the electrochemical properties were tested and studied by using the MnO@C-AH composites as lithium-ion batteries?LIBs?anode materials.?3?The manganese alginate aerogels were prepared by ion exchange and freeze drying methods with the sodium alginate?SA?as carbon source and template.The carbon aerogel and manganese oxide composites?CA@MnO?were obtained by the pyrolysis of manganese alginate aerogels at high temperature in the atmosphere of Ar/H₂.A series of characterizations for the structure and morphology of the CA@MnO composites were carried out.Moreover,the electrochemical properties were tested and studied by using the CA@MnO composites as lithium-ion batteries?LIBs?anode materials.