Synthesis And Electrochemical Performance Of Manganese Silicates As Anode Materials For Lithium-ion Batteries

As a new type of green energy,the lithium ion secondary battery has been attracted widespread concern and research,and gradually used in hybrid cars and other large equipment.As an important part of the lithium-ion battery,the selection of anode electrode materials has a great influence on the electrochemical properties of lithium-ion batteries.However,the carbon material using in industry application has lower capacity,which cannot meet the requirements for high energy density of energy.Therefore,currently the focus of research is trying to explore new anode materials which possess higher theoretical capacity,low cost synthetic and environmental friendly.In this paper,we using a relatively simple operation successfully synthesized a new anode material-manganese silicate,and then carbon-coated with glucose,the carbon-coated material behaving high specific capacity and excellent long cycle stability.Furthermore,we also explore a new method for preparing the amorphous manganese silicate by simple boiling method and successfully synthesized,the electrochemical properties have also been tested.The main contents are as followed:（1）Manganese silicate was simply fabricated by the reaction between Na₂SiO₃·9H₂O and MnCl₂·4H₂O.The carbon-coated manganese silicate acting as anode material for lithium storage exhibits outstanding rate performance and high-rate cycling stability.The reversible capacities of 323,293,261,227 and 176 mAh/g achieved at the corresponding specific currents of 100,200,400,800 and 1600 mA/g are greatly superior to those of the commercial graphite,and the reversible capacity of 343 mAh/g after 400 cycles at 500 mA/g is much higher than that of LTO.Combining detailed characterizations with electrochemical measurements revealed that the uniform carbon coating around the manganese silicate nanoparticles as conductive material and the formation of lithium silicate as solid electrolyte are responsible for the excellent performance.The carbon-coated manganese silicate could meet the requirement for fast charging/discharging Li-ion batteries.（2）Amorphous manganese silicate was fabricated by simply heating a mixture of Na₂SiO₃·9H₂O and MnCl₂·4H₂O in boiling water（called water-boiling treatment）.Even after being coated with carbon at 700℃ employing glucose as the carbon source,the silicate is still in the amorphous state.The electrochemical performance of the carbon-coated amorphous silicate as an anode material for Li-ion batteries was evaluated.The carbon-coated product with a water-boiling time of 4 h exhibits excellent rate performance and high-rate cyclability,after 400 cycles at 500 mA/g,the reversible capacity is still 421 mAh/g for S4C-600.The amorphous silicate with a porous structure and a large specific surface area is beneficial to Li-ion transportation,and the homogeneous carbon coating around the silicate nanoparticles as a conductive material is conducive to improving their electronic conductivity.